Thanks again @South Main Auto Repair for fixing my Cherokee! The 4.0 ran smooth as silk driving back to PA, no money light! Wife says I should keep it now that you fixed it... LOL
rtchrg440 sell it a run, run fast. I have been a Jeep owner for over 20 years...and still own two in the Family. I swear those vehicles are designed to make money for the Chrysler company in parts sales AFTER the initial vehicle sale.
I know what you mean. I was a faithful Toyota owner before I bought this XJ, never had a vehicle like this that always seems to need a part every other month. One thing I will say, I usually buy aftermarket parts for the Jeep to save money, and at least 50% of the time the part has failed in a year. So I really bought the part twice, and probably didn't save in the long run. Frustrating! This crank sensor was aftermarket (either from RockAuto or AutoZone, can't remember), and it was doing this from the beginning. I shot a ton of other parts at this Jeep thinking it was a legit misfire.
rtchrg440 I only go OEM for my Jeeps either new or the used parts market - from junkyards - that has recently and robustly sprung up on the internet in the last few years like partsmarket. Mopar rear drive shaft new $895, from the salvage yard $65 plus $50 for shipping and I can get one from States not in the rust belt. I tried the Chinese made parts once. Part was a rear window strut that holds up the window. Lasted 18 months. Then I purchased Mopar OEM and it so far has lasted 4 years.
rtchrg440 nice Jeep! I have a 2k XJ myself and I love it. I have the OEM sensor and after this video I might swap it in, got that tiny flutter going on but no money light. Have a great weekend.
What an odd and annoying fault because it is so indecisive. As someone else mentioned, the transient spikes after the new sensor were fitted seemed lower, so maybe it was just a connection resistance issue or the new sensor might have a low value capacitor in it as a filter. It could possibly be one of those things that didn't occur when they were writing the software, but as age crept in it became an issue. There are some industrial control systems where you have to use a specific brand of contactor because the auxiliary contact closure timing is so critical that the software shuts off the machine and flags it as a contactor fault if the wrong brand of contactor is used.
It's really annoying when the timing isn't critical to the job the machine is doing, it's just critical to the time that was programmed. Programmers set it up to see a value in a very short time like .002 seconds when it wouldn't matter if it took 5 seconds.
@@tiredoldmechanic1791 The rise/fall time on the aftermarket sensor most likely is causing the computer to get confused as it's not seeing a sharp transition to measure rotational acceleration. This allows it to run but not monitor itself. I suspect the "square" edge of the signal starts to round over. The programmer needs something consistent to trigger off to accurately measure acceleration. If we only cared about rpms I would agree that it's the programmer's fault. I'm a hardware guy and like to blame software too but this time it is not the programmer's fault. This suspected rounding (rc effect) is only visible if zoomed in. Then again I could be wrong as the data from the video is zoomed out way too far.
It is one thing to shoot parts at it when nothing shows wrong but another to look up data talk to others and then take an educated guess very well done.
When I trained as a tech in the military we had a W.A.G. and a S.W.A.G. Wild assed guess or a scientific wild assed guess. ;) This was one of the later. I know, old video, but I enjoy watching them when they pop up in my feed.
Thank you for the fix! I had the same problem with my 1998 Jeep Wrangler 4.0 . Only 3000 miles on a complete reman. longblock, ran like a top but the check engine light came on and I scanned it and the codes showed multiple misfires across all 6 cylinders. It still ran silky smooth. I ran across this thread yesterday and so I removed the newer aftermarket crank sensor and put in a used oem crank sensor I had laying around and it cured it. No more codes. Now I can get this Jeep smog tested tomorrow so I can get it re-registered. One thing I noticed is the magnetic tip on the OEM crank sensor is very strong and can pick up a wrench, but the aftermarket version can bearly pick up a screw. Thank you so much for sharing your technical knowledge, you saved me some money for sure!
I have a 98 4.0 With a new motor Also , I can’t get a oem cps so I put a hvwells one in and still has a misfire , she’s been in the shop for a few days , I hope they figure it out
awesome diagnosis and work. I actually did one of these jobs while I was in a high school auto shop class! of course, My school didn't have any real awesome scope software or anything. After WEEKS of testing with a DVOM, I had isolated the crankshaft sensor, and replaced it and verified the fix. My shop teacher was super impressed with me. I owe all my success to the man.
Nice video on using what I teach as "educated guessing". Your video example is "NEEDED" is the "toolbox" of technicians or DIY wrench turners. In the real world sometimes things just don't make sense. Theres no visual or measurable evidence to go from and to fix the problem we turn to what I call "the medical method"....This is where you consider what worked for a 100 other people get healed and go for it. There is still much thought and consideration put into this decision based on research, peers and OEM support. Just reminds me how glad I am to be a technician most often working from pure evidence and not "practicing medicine"! Once agian, great job and I bet you would like my "Every Mechanic Should know This" Playlist. I'm a fan of South Main Auto videos for sure....Coach Conley
I've been chasing this same problem for a year. I have had 4 CPS installed during that time, and only when I finally got a Mopar part, was it resolved. The previous owner who swapped the engine in my wrangler, dropped one of the flywheel/torque converter bolts inside, it rode around in one of the grooves of the flywheel eventually hitting the CPS and breaking it (twice) before I discovered it. The CPS did continue to work while missing plastic! Eventually I discovered that issue, removed the bolt, and replaced the CPS with a Napa premium part. From day one that sensor always triggered the misfire code at 3000 rpm and above. I looked everywhere else assuming it was not related to the CPS. Now after seeing this video I went ahead and ordered a Mopar part and after 4 days the misfire code never happened. I can finally engine brake through the mountains around here without dreading the flashing misfire light. I watched this video during an international flight and then ordered the sensor as soon as I got home. Glad I have been subscribed to you for some time now.
That's why working on vehicles can be fun. You give something a try when your out of options and it works. That's a good feeling. Great information in the description box. That's going to help a lot of people. Another crazy TH-camr out the door happy!
I remember a story where a huge diesel motor on a giant cruse ship wouldn't run. None of the technicians could figure out why. They gave up and called in an old retired dude. He looked at a while. Pulled a large hammer out a bag and gave it a hard WACK! It Stared up and ran perfectly. When he gave them the Bill it was for $10,000.00. They all freaked. "you didn't do anything" they said. Give us an itemized billing statement! The bill he produced said. One hammer blow: $8.99 Knowing where to hit: $9,991.01
"knowing where to hit" is ABSOLUTELY RIGHT! In so many cases we have to draw from our experiences, Eric knew which part to change and the old man knew where to hit. 1 + 1 is 2 because my 1st grade teacher taught me so. NEXT!
Eric I was wondering on that crank sensor do you think that the aftermarket sensor is a different kind of sensor then the OEM I know there are two different kind of sensors. One can be hall effect sensor and honestly I am not remembering the other type of sensor. Just a thought
That's unlikely, my friend. You are one of the best mechanics that I've ever seen. I have been doing this thing for 38 years and you're. good. And fun.
Add Gm fuel pumps only & MAF sensors on GM cars. Been burned too often with non OEM parts. Cost more, but I only want to do it once. Especially dropping the tank for a fuel pump replacement
I've found that gut and others experiences have bettered the high priced scanners alot of the time most customers do not understand the scanner jargon great video Eric O
Thanks Eric. You have helped me out of a pickle with the wife’s Chrysler minivan more than once. (2009 3.8L) hope you make more videos of them. I enjoy watching you work on any vehicle. Including this one.
I work at an auto parts store, and no lie, this era Jeep 4.0L is literally 40% of our business. If you look at our shelves, we are jammed full with Jeep stuff. Every single day we get dozens of calls from people needing parts for these heaps. I'm not making this up. Jeep keeps parts stores in business! I'll never own one, but from a job security standpoint, I'm glad they exist.
Another case of a stupid system telling you something is wrong when it is not. How much did the owner spend at the multiple shops where the fix was just to make the false message go away? Even the diagnostic system doesn’t know. Good on you Eric! Wish you were nearby to diagnose my cars!
Found this video after going thru the same thing on my 96 XJ, occasional high rpm check engine light with random misfire codes but it always ran smooth. Swapped the CPS sensor with OEM mopar and it seems to fix it so far. This video provided the needed confirmation :).
Nice to see you do it my way sometimes! I do it because I'm certainly no pro, have no expensive analytic tools (but appreciate those who do!) and it's a constant weighing of paying for labor vs parts. I'd pay for the former if I got as much out of it as your customers do, Mr O...if there are any here in MN, commenters, let me know.
My guess before the video was the crankshaft possition sensor, but like the guy said I didn't see any discrepancies when the Pico was reading it. I loved the video a big thumbs up and subscribe to this guy
I am in Buffalo NY with the exact problem. Installed an aftermarket sensor a few months ago. I think this video just saved me a lot of time and effort! Would love to have you do my rear main seal for me
Eric, you ever wrap a wire several times around a screwdriver or socket and the touch the striped ends to the positive and negative to magnetize that socket or screwdriver. Work great when you have to hold on to nuts and bolts from a distanced with an extension.
Just changed my crank sensor today (Mopar OEM). I strongly recommend taking five minutes to drop the driveshaft at the differential. I swung it over toward the passenger side and ziptied it to the catalytic convertor. I was then able to gain much better access to the sensor bolts. I only had to use one extension and a wobble joint and was actually able to reach around the exhaust and get both hands up into the area to start the bolts when reinstalling. I still had to work by feel but it was much easier than fighting the driveshaft. I hope this helps those of you facing this repair.
Eric sometimes it's better to be lucky than good! We all have done it and if u say you haven't your either lying or u don't work on enough cars. Have a great day and GOD BLESS AMERICA. GO CUBS! Keith
Yes! Great video, had random cylinder misfires just like this on a 2001 4.0 Jeep Wrangler with AT. Had a new aftermarket crankshaft position sensor, all the other things too, new plugs, new coil, checked all injectors for resistance, etc etc. Saw this video along with another one from Scanner Danner, both said to use the factory original Mopar part, so I took the chance, replaced the aftermarket crankshaft position sensor with the factory piece and problem solved! Thanks for posting the video! Great videos as always!
TL;DR: The old sensor put out a good square wave pattern but was inaccurate/inconsistent in ON time. Thanks for the captures! I've never actually used a PicoScope before. I downloaded the software to look at your captures and gotta admit it's bloody cool. I was able to do measurements and analysis in about 5 minutes whereas it would have taken 20+ painstaking minutes with my Verus... So you can't compare times between old and new. You're not running at the same RPM so times are irrelevant. You have to compare degrees of crankshaft rotation as that's the only thing that is constant. I measured the width of 4 pulses on the crank pattern on both the old and new waveforms. I used the same tooth every time to be consistent. On the old sensor I got 1.427*, 1.575*, 1.562* and 1.579*. On the new waveform I got 1.16*, 1.16*, 1.109* and 1.111*. On the old sensor, each pulse lasted more degrees of crankshaft rotation than the new sensor. I imagine that's not what set the misfire. No two sensors are exactly the same so that would probably get processed by a crank relearn. HOWEVER... the pulses are pretty inconsistent on the old sensor whereas they are VERY consistent on the new sensor. The difference between the shortest pulse length and longest pulse length on the old sensor is 0.152 degrees. Even after going back through the new trace and looking at way more samples the largest difference I could find between pulse lengths was 0.011 degrees. That's going to be what's causing the reported misfire. The time delay between when the tone wheel notch passes by the old sensor and when the sensor is able to fully turn on and off its transistor just is not consistent.
I absolutely love this engine. I've had 3. Yes odd issues here and there but reliable and smooth regardless how many miles were on it. I took one to 356k, one to 375k and the last one was totalled in 2019 with just under 340k with a mint leather interior. Yes, that crankshaft sensor caused an issue on my 1997 Grand Cherokee TSi. Just stopped on me one day and I had no idea which direction to go. Luckily I had an uncle who worked at the Chrysler Jeep dealer in town and he helped me over the phone. I admit hearing those 6 cylinders firing up brings a tear to my eyes. Reminds me of years of worry free driving across the southeast. I drove one from 2000-2019 (2 1997 ZJ TSi and 1 2003 WJ Laredo). Always looking for a good one to keep a few years 1996-2004 only. Hope you and Mrs. O. had a good New Years Weekend. 🎉
This may surprise you Eric but your guesses are more often than not better the most mechanics or technicians knowledge today. Keep knocking out those cars and enjoy your days
Had a similar situation. Friend took his 4.0 Cherokee into the shop because of check engine light at highway speeds. Shop said it was indicating all 6 cylinders were showing a "spark" miss and they began replacing parts. ECM and Coil Pack and other parts to the tune of over $2650.00 in parts My friend asked if I could check with the shop and so I called just casually asked what waveform they were getting generated when they tested They said it was great and had never showed a bad waveform and that was what throwing their troubleshooting off. I quietly suggested that they might try changing the crankshaft sensor ( which they had not done to this point. It is not my vehicle or my right to get into the middle of the problem). Long story short, they changed the crank sensor and the wave forms returned to normal. Sadly, of course they just added the cost of the crank sensor to the $2650.00 parts plus labor bill telling my friend that somehow the "ECM had defaulted in it's code and caused other parts such as the coil pack and crankshaft sensor to fail". I explained to my friend that such thing just could not happen and if he wanted to dispute the charges I would be willing to help him but he would need to start the process not me. He never did anything about it so he received an education, I received an education and I am sure the shop received an education. Aloha from Maui
So, what is the ethical way to run through this parts changing fusillade, short of bringing it to Eric "the Swami" @ SMA ? I got $9,899.00 hammers too, but feel bad using them.
Classic video. I had a grand Cherokee similar issue. It would run like crap while crossing railroad tracks. Bunch a shops couldn't figure it out. Customer brought it in, through a monitor on it and cranked it up. Went behind the truck and climbed on the ball mount and started jumping up and down. Jeep began running like crap. I said crank sensor. Took a long screwdriver and then tapped the sensor and again ran like crap. I feel better about your guesses than other peoples facts. ;)
Good job on getting a Mopar sensor. I had a 97 grand Cherokee 4.0 and I had a similar issue and I replaced the crank sensor with an aftermarket. It ran great for about a month then the same issue. I got a Mopar one and never had the issue again. I learned Jeep's are picky with sensors.
This is what they call "an educated guess"!! Nothing wrong with that. Good work. I think this is a very good looking car, Been looking forone for a while here in Sweden. But hard to find in good shape. Good work, love your channel!
Wow Never seen a Missfire On all 6 cylinders before And the Engine Run Smooth as Butter that is Interesting Defenitly looks like a Crank Sensor Failure good Video as Always Eric O great find on this video @SouthMainAutoRepairLLC
THANK YOU, THANK YOU, THANK YOU, Mr Polish Guy! Just fixed my Plymouth Neon with the same shit (money light, flashing, P0300) after replacing CKP, CMP, plugs, wires, Coils, fuel pump, fuel filter, PCM, O2s, PCV, Intake gasket, Injectors and many cuz words nothing. After watching this video I ordered a MOPAR CKP and problem SOLVED! Thanks again Eric O.
It's so good to have a lift, It was a full-on pain in the royal ass for me to install that sensor..kind of reminded me of that old school board game operation.
I cant believe I heard Eric O. Say that he was making an educated guess??? Lol. I could see the legitimate agony he was feeling by his facial expressions when he made that statement. BUT that's exactly the reason that people TRUST and APPRECIATE his candor about his work. There obviously was something wrong in the circuitry of that aftermarket sensor that was telling the ECM bogus information. I am surprised you couldnt test that old sensor once it was out of the jeep to see some form of bad communication coming from it in comparison to the new one. Not sure how to read digital communications so ill leave that up to the expert Eric O. I will say it was nice to see a video from a TH-camr's car as we like to give back to the SMA channel by provide good subjects for diagnostic videos. I hope more TH-camrs bring their car to Eric. He deserves the business.
Could have been something as simple as that tiny bit of noise causing the problems. Improper shielding in the aftermarket sensor? Who knows? Sometimes cars and trucks hate aftermarket parts and you'll hear a distinct "Patuewieeeeee..." sound as it spits it back out like a 1.5 year old eating his veggies.
I hate guessing myself. We want data to back up our claims. My theory is that the sensor it's self was on it's last legs internally (doorman maybe? or BWD) when it was put in and the coil inside is shorting it's self. Anyway awesome video as usual Eric. Keep it up!
Missing Misfire Mystery Solved? Once again a great video and the fact that you were "guessing" doesn't worry anyone who know that your guesses are based on a solid foundation of both knowledge and experience and you can guess on my car any day. By the way I noticed that when you start the video and show the cam/crank relationship at idle the cam signals are lining up with the fourth crank signal but when you rev up the engine the cam signal now is lining up on the third crank signal. This might explain why the misfire code are being generated. I notice that after the crank sensor was replaced the cam signal stays with the fourth crank signal even at higher RPMs. Please check it out and let me know what you think. Keep up the awesome videos they are teaching me alot and you crack me up with your terminology and the ease and enjoyment that you get when working on cars. Thanks so much.
Having same issue with a 01 Jeep Wrangler at the shop. At 3K RPM shows ghost misfires. I put an aftermarket sensor and didn't help, guess ill go OEM. I noticed you didn't relearn the misfire counter when installing the new crank sensor. You can see and your scanner it says adaptive learned no. That's why it wasn't showing misfires. I know because when I changed the crank sensor it wasn't misfiring again until it learned the misfire monitor. You fixed it though since the vehicle never returned.
I know three retired Chrysler engineers who were very familiar with the JTEC PCM. While all generally praised it, the word around Auburn Hills was that JTEC was an abbreviation for "jus' tryin' to be an engine controller". I wouldn't be surprised to find a line of code someplace that checked for Brand X parts!
There used to be a video somewhere on YT that used waveforms etc to go deeply into the differences between OEM and aftermarket crank sensors on Jeeps. I can't find it any more, but I recall that they *did* pinpoint differences that could account for why Jeeps are so picky about them, and they weren't in any way obvious.
My 02 wrangler 4.0 had the same problem. Found out that the sensor has a felt pad on it you need to mash it into the flywheel and it wipes the felt off. The oem came with instalation instructions saying to do it, reinstalled the aftermarket one mashing it in and worked perfectly, couldn't find anything anywhere online to help.
I have seen this on multiple Cherokees. The first one had me banging my head against the wall trying to figure out the problem. Came to realize after that the truck originally did not start and the customer had brought it to a shop where an aftermarket sensor was installed. Long story short, my cam/crank waveform was obviously fine as was the crank pattern itself to my eyes. "Guessing" that the aftermarket sensor was the culprit, I changed it with a dealer part and problem was solved. Only thing I can think of is the air gap may be different between it and the aftermarket part. Other than that, I have no idea what else would cause this.
Even to the most casual observer the answer was apparent it was gyroscopic instability produced by a low center of gravity, or the knueter valve was clogged up :o) Way to SWAG the problem Eric
Hi Eric, very interesting case, I downloaded the waveforms and the only difference I could find was that the old sensor at idle and 2500 rpms the square signals from crank were longer time base wise idle= 697 us Old to idle= 472 us new at 2500 rpms old =216.9 us new= 133.3 us. Would that be enough to create false misfires counters?
MrBorntoroll the thing here is that there was no actual misfires, so this is more of a software glitch than an actual misfire. All cylinders showed misfire only on software.
I mean with the firing event we would have some more measurments as the pcm measures speed of the crankshaft after cyllinder firing to flag a missfire.
Ok. We kinda have spark events. The theory: if PCM counts time of crank rotation after spark event not until every next HIGH hump but until next for ex "big low gap and HIGH hump" (to give time for combustion to occur) then we can see that with old sensor be get quite bigger (in ms) time delay which can be calculated as missfire if PCM wants to see shorter time. The bad news: the theory doesn't work during idle.
yes the millsec would make a differance, since no ditributor to turn then im guessing the random delay in the crank sensor is making the light come on :) great work as allways!
I had a similar symptom with a Honda accord. Misfire that got incrementally worse over a years time. Did all the checks, diagnosed it as a bad exhaust valve. Put a head on it (correct diagnosis, the exhaust valve had part of it eroded away in a neat little perfectly round pac man-esque bite). The similarity was when it was done it ran flawlessly. At RPM above 1000 it would flash the money light and set a misfire code, but it was running perfect (as a honda can). For 2 days it drove me nuts, had to walk away and do other payers as i contemplated this bizarre turn of events. The supervising super tech at the company did all the same tests i did, called tech support. No dice. I started exploring EVERY possible data parameter. As i stumbled through every possible menu in the scanner looking for ANYTHING that could help, i find an option buried in the engine side (Snap on scanner) "reset engine adaptives". CLICK!. THE PROBLEM WAS GONE. I was thinking it was something like that on Eric O's headache. First time i had ever seen that as a menu option.
I've heard from different sources that the aftermarket sensors have some kind of weirdo diode in them or something like that but in the process of heating and cooling this diode for the 5 volt reference ends up popping and it allows it to bleed through the reference wire essentially giving it 2 signals it's throws the computer out of wack but when you go to look at through the Pico you're seeing the direct line in and that's why you can't see a fault you're not seeing what's bleeding back to the computer if that makes any sense.. at least that's what was explained to me.... just an FYI for your information keep up the good work Mr.O
The Mopar Crank sensor using a specific code and pulse to communicate with the PCM (think of it like to encrypted phones taking to each other). The aftermarket ones are close but not enough to be registered 100% with the PCM. So there Crank sensor is saying "We're all good dawg" but the PCM is only recieving "We'r al d daw." Some are so off they won't even start even though the scope looks good. Just wanted to add if you have to but aftermarket sensors the ones that will give you little to no trouble is Standard Motor Products. This goes for ALL MOPARS. A few of us guys on the forums fingered out why they didn't work when we were watching the programming in the PCM itself.
From an electronics point of view, I can't find the specs for the picoscope, but I suspect that the aftermarket ckp is producing noise on the signal line that is too fast for the Pico to catch. Next time I get one of these in the shop I'm going to use a 200mHz scope on it and see what there is to see. Maybe it's nothing but, that sensor HAS to be producing something the ECM doesn't like. We just have to find it.
2001 GC with lots of pissy-little-'minor'-tooling-around-getting-it-right-things-that-annoy-me-so-it-doesn't-let-me-down-&-I-know-things-are-right-issues. They're not bad vehicles, just vehicles that need maintenance! Liked & subscribed! TYVM for an informative channel. O2 sensors are another red headed stepchild for these as well as clean battery terminals. I've seen on a few occasions these Jeeps are fussy about very clean voltage & copper core spark plugs. No better plugs for them.
These are the cars that don't play fair. Tests perfectly yet is bad. That's why it's nice knowing a few other techs that you can share cases with. Identifix can come in handy for these problems occasionally but between me and a buddy of mine one of us has usually run across these issues at some point.
Hi Eric. Downloaded the files @2500 rpm and used Pico measument tools. Old sensor duty cycle is 10,28% New is 11,1%. 7% difference in pulse width -> upto 25 degree variation to angle speed dRpm. Old sensor became more insensitive detecting a flywheel teeth. Turned on later and turned off a earlier. Could this be the diagnosis?
Awesome! I wonder if the magnet on the crank starter wheel gets weaker with time and heat, thus the heavier wound and more sensitive mopar sensor is the only one accurate enough?
Thats what I thought. That maybe the aftermarket sensor is manufactured slightly differently that maybe the PCM wasn't getting the full value it was expecting.
most people say "i dont know" when asked when was the last time spark plugs were done (and on this....people forget the cap and rotor is a wear part) so i usually will pull a plug to have a gander . but ya.... ive shotgunned my own cars ignition (dont have time, and dont want to WORK on my own shitboxes) 99 GM 3.1...... waste spark can go F it self . new plugs and wires.... still had a soft miss that the CEL didnt light for but the old plugs WERE quite old, and the wires 10 years old.... . turned out..... bad coil then i tightened the bolt too much because it was -30f.... and cracked that coil . then i got a bad coil..... that split in half turned my car into a 4 banger..... limped my way into work . and finally..... ive had NO issues for 80,000 miles and now its about time to do the plugs again... . PS on my 97 4.0 jeep..... i have a miss that cant be felt (some times cly 5, some times random multi, or sometimes 2 5 and random) but its usually going down a hill, with like 2 gallons of gas in the tank.... . throws the code with in 200 feet of the same hill..... . doesnt seem to do it (as often) when it has 1/4+ tank of gas . oh well..... its a mopar..... reset the code, keep driving till something changes / gets worse enough to fix
There are times when an "experience based" approach is necessary. I have worked on wind turbines when nothing was out of specs and everything was apparently good. But the turbine would just not come online. Dig back into my experience and I just knew that if I replaced part x, then it would come online. Sometimes that is the only way to get it done. If it works, and the customer is happy, don't sweat it. You spend a ton of time of troubleshooting customer cars, and ensuring that you get the exact problem nailed down and fixed right. If there is an occasional time where you can swap a common part and get the car fixed and back on the road without spending two or three hours of shop time, all based on your experience, then so be it. You will get the car back to the customer faster and with a smaller repair bill, and you can get on to the next one. It is the odd ball problems that really require your level of expertise in troubleshooting and attention to detail to iron out.
Thanks again @South Main Auto Repair for fixing my Cherokee! The 4.0 ran smooth as silk driving back to PA, no money light! Wife says I should keep it now that you fixed it... LOL
rtchrg440 sell it a run, run fast. I have been a Jeep owner for over 20 years...and still own two in the Family. I swear those vehicles are designed to make money for the Chrysler company in parts sales AFTER the initial vehicle sale.
I know what you mean. I was a faithful Toyota owner before I bought this XJ, never had a vehicle like this that always seems to need a part every other month. One thing I will say, I usually buy aftermarket parts for the Jeep to save money, and at least 50% of the time the part has failed in a year. So I really bought the part twice, and probably didn't save in the long run. Frustrating! This crank sensor was aftermarket (either from RockAuto or AutoZone, can't remember), and it was doing this from the beginning. I shot a ton of other parts at this Jeep thinking it was a legit misfire.
rtchrg440 I only go OEM for my Jeeps either new or the used parts market - from junkyards - that has recently and robustly sprung up on the internet in the last few years like partsmarket. Mopar rear drive shaft new $895, from the salvage yard $65 plus $50 for shipping and I can get one from States not in the rust belt. I tried the Chinese made parts once. Part was a rear window strut that holds up the window. Lasted 18 months. Then I purchased Mopar OEM and it so far has lasted 4 years.
rtchrg440 nice Jeep! I have a 2k XJ myself and I love it. I have the OEM sensor and after this video I might swap it in, got that tiny flutter going on but no money light. Have a great weekend.
stinking "aftermarket junk". as eric and many of us say.
What an odd and annoying fault because it is so indecisive. As someone else mentioned, the transient spikes after the new sensor were fitted seemed lower, so maybe it was just a connection resistance issue or the new sensor might have a low value capacitor in it as a filter. It could possibly be one of those things that didn't occur when they were writing the software, but as age crept in it became an issue. There are some industrial control systems where you have to use a specific brand of contactor because the auxiliary contact closure timing is so critical that the software shuts off the machine and flags it as a contactor fault if the wrong brand of contactor is used.
It's really annoying when the timing isn't critical to the job the machine is doing, it's just critical to the time that was programmed. Programmers set it up to see a value in a very short time like .002 seconds when it wouldn't matter if it took 5 seconds.
@@tiredoldmechanic1791 The rise/fall time on the aftermarket sensor most likely is causing the computer to get confused as it's not seeing a sharp transition to measure rotational acceleration. This allows it to run but not monitor itself. I suspect the "square" edge of the signal starts to round over. The programmer needs something consistent to trigger off to accurately measure acceleration. If we only cared about rpms I would agree that it's the programmer's fault. I'm a hardware guy and like to blame software too but this time it is not the programmer's fault. This suspected rounding (rc effect) is only visible if zoomed in. Then again I could be wrong as the data from the video is zoomed out way too far.
Shit up Engineer.
Electronics are fickle things... It's almost like programmers don't give enough leeway for things as they age. But, it is what it is I suppose
I have shot part at a car a few times and that's was the problem fixed😂
It is one thing to shoot parts at it when nothing shows wrong but another to look up data talk to others and then take an educated guess very well done.
When I trained as a tech in the military we had a W.A.G. and a S.W.A.G. Wild assed guess or a scientific wild assed guess. ;) This was one of the later. I know, old video, but I enjoy watching them when they pop up in my feed.
Thank you for the fix! I had the same problem with my 1998 Jeep Wrangler 4.0 . Only 3000 miles on a complete reman. longblock, ran like a top but the check engine light came on and I scanned it and the codes showed multiple misfires across all 6 cylinders. It still ran silky smooth. I ran across this thread yesterday and so I removed the newer aftermarket crank sensor and put in a used oem crank sensor I had laying around and it cured it. No more codes. Now I can get this Jeep smog tested tomorrow so I can get it re-registered. One thing I noticed is the magnetic tip on the OEM crank sensor is very strong and can pick up a wrench, but the aftermarket version can bearly pick up a screw. Thank you so much for sharing your technical knowledge, you saved me some money for sure!
I have a 98 4.0
With a new motor Also , I can’t get a oem cps so I put a hvwells one in and still has a misfire , she’s been in the shop for a few days , I hope they figure it out
awesome diagnosis and work. I actually did one of these jobs while I was in a high school auto shop class! of course, My school didn't have any real awesome scope software or anything. After WEEKS of testing with a DVOM, I had isolated the crankshaft sensor, and replaced it and verified the fix. My shop teacher was super impressed with me. I owe all my success to the man.
Key word here is EDUCATED guess, there is a difference vs just a wild guess!
SWAG vs pure wild guess....
Difference being no beard strokeing
Indeed
He sure keeps that old Jeep clean! Well done, Dr. O!
Well done Eric, yet another satisfied customer brought in by You Tube. Great video!!
An experienced based guess is what people pay you for! Your knowledge is valuable!
Nice video on using what I teach as "educated guessing". Your video example is "NEEDED" is the "toolbox" of technicians or DIY wrench turners. In the real world sometimes things just don't make sense. Theres no visual or measurable evidence to go from and to fix the problem we turn to what I call "the medical method"....This is where you consider what worked for a 100 other people get healed and go for it. There is still much thought and consideration put into this decision based on research, peers and OEM support. Just reminds me how glad I am to be a technician most often working from pure evidence and not "practicing medicine"! Once agian, great job and I bet you would like my "Every Mechanic Should know This" Playlist. I'm a fan of South Main Auto videos for sure....Coach Conley
Shane Conley yet another example of ‘it works in practice, but does it work on paper?’
I've been chasing this same problem for a year. I have had 4 CPS installed during that time, and only when I finally got a Mopar part, was it resolved. The previous owner who swapped the engine in my wrangler, dropped one of the flywheel/torque converter bolts inside, it rode around in one of the grooves of the flywheel eventually hitting the CPS and breaking it (twice) before I discovered it. The CPS did continue to work while missing plastic! Eventually I discovered that issue, removed the bolt, and replaced the CPS with a Napa premium part. From day one that sensor always triggered the misfire code at 3000 rpm and above. I looked everywhere else assuming it was not related to the CPS. Now after seeing this video I went ahead and ordered a Mopar part and after 4 days the misfire code never happened. I can finally engine brake through the mountains around here without dreading the flashing misfire light. I watched this video during an international flight and then ordered the sensor as soon as I got home. Glad I have been subscribed to you for some time now.
That's why working on vehicles can be fun. You give something a try when your out of options and it works. That's a good feeling. Great information in the description box. That's going to help a lot of people. Another crazy TH-camr out the door happy!
Will have to remember this fix! I have the exact same jeep with 193k on the clock and counting, been the best vehicle I have ever owned.
Once again, experience, and knowledge of the trade, wins over a stubborn vehicle.
Good job as usual
I remember a story where a huge diesel motor on a giant cruse ship wouldn't run. None of the technicians could figure out why. They gave up and called in an old retired dude. He looked at a while. Pulled a large hammer out a bag and gave it a hard WACK! It Stared up and ran perfectly. When he gave them the Bill it was for $10,000.00. They all freaked. "you didn't do anything" they said. Give us an itemized billing statement! The bill he produced said. One hammer blow: $8.99 Knowing where to hit: $9,991.01
Dj Quack lmao that made my day
I love it!!!
"knowing where to hit" is ABSOLUTELY RIGHT! In so many cases we have to draw from our experiences, Eric knew which part to change and the old man knew where to hit. 1 + 1 is 2 because my 1st grade teacher taught me so. NEXT!
I saw the video that story came from, definitely priceless!
Eric I was wondering on that crank sensor do you think that the aftermarket sensor is a different kind of sensor then the OEM I know there are two different kind of sensors. One can be hall effect sensor and honestly I am not remembering the other type of sensor. Just a thought
That's unlikely, my friend. You are one of the best mechanics that I've ever seen. I have been doing this thing for 38 years and you're. good. And fun.
That is one clean looking engine compartment, even the undercarriage looks dry. Loved that.
When it comes to crank/cam sensors I learned a long time (the hard way)ago to only use OEM.
Those 4.0's love Mopar sensors only.
Ben R Fords also.
Add Gm fuel pumps only & MAF sensors on GM cars. Been burned too often with non OEM parts. Cost more, but I only want to do it once. Especially dropping the tank for a fuel pump replacement
I've found that gut and others experiences have bettered the high priced scanners alot of the time most customers do not understand the scanner jargon great video Eric O
another awesome video by Eric O....looks like your parts cannon has some serious experience to get it right on the first try...
some serious aim on thats parts cannon... Laser scope i think.
Jeeze, the engine bay is clean on that old Jeepster. He must be crazy.
Noooooo that’s a cherokee..... you can’t wear a jeep hat and get that wrong!!
Thanks Eric. You have helped me out of a pickle with the wife’s Chrysler minivan more than once. (2009 3.8L) hope you make more videos of them. I enjoy watching you work on any vehicle. Including this one.
Eric, I like how informative your videos are, plus I like when I hear that you help out other channels with their diagnosis ( Will R.A.) COOL
I work at an auto parts store, and no lie, this era Jeep 4.0L is literally 40% of our business. If you look at our shelves, we are jammed full with Jeep stuff. Every single day we get dozens of calls from people needing parts for these heaps. I'm not making this up. Jeep keeps parts stores in business! I'll never own one, but from a job security standpoint, I'm glad they exist.
Vercus100 remember how many of these things are out there ...
Reminds me of the educated guess you made on the Chivy Colorado. It's beyond cool that we can share waveforms like this. Well done Dr. O. Thanks!
Another case of a stupid system telling you something is wrong when it is not. How much did the owner spend at the multiple shops where the fix was just to make the false message go away? Even the diagnostic system doesn’t know. Good on you Eric! Wish you were nearby to diagnose my cars!
Found this video after going thru the same thing on my 96 XJ, occasional high rpm check engine light with random misfire codes but it always ran smooth. Swapped the CPS sensor with OEM mopar and it seems to fix it so far. This video provided the needed confirmation :).
My Grand Cherokee 4.0L did the same thing and it was the Crank Positing Sensor. These 4.0L Straight 6 are noted for these.
Nice to see you do it my way sometimes! I do it because I'm certainly no pro, have no expensive analytic tools (but appreciate those who do!) and it's a constant weighing of paying for labor vs parts. I'd pay for the former if I got as much out of it as your customers do, Mr O...if there are any here in MN, commenters, let me know.
My guess before the video was the crankshaft possition sensor, but like the guy said I didn't see any discrepancies when the Pico was reading it. I loved the video a big thumbs up and subscribe to this guy
I am in Buffalo NY with the exact problem. Installed an aftermarket sensor a few months ago. I think this video just saved me a lot of time and effort! Would love to have you do my rear main seal for me
Nothing wrong with an educated guess now and then especially since you're so experienced, and as it turned out you were right. Thanks for the video.
Eric, you ever wrap a wire several times around a screwdriver or socket and the touch the striped ends to the positive and negative to magnetize that socket or screwdriver. Work great when you have to hold on to nuts and bolts from a distanced with an extension.
Just changed my crank sensor today (Mopar OEM). I strongly recommend taking five minutes to drop the driveshaft at the differential. I swung it over toward the passenger side and ziptied it to the catalytic convertor. I was then able to gain much better access to the sensor bolts. I only had to use one extension and a wobble joint and was actually able to reach around the exhaust and get both hands up into the area to start the bolts when reinstalling. I still had to work by feel but it was much easier than fighting the driveshaft. I hope this helps those of you facing this repair.
Eric sometimes it's better to be lucky than good! We all have done it and if u say you haven't your either lying or u don't work on enough cars. Have a great day and GOD BLESS AMERICA. GO CUBS! Keith
Yes! Great video, had random cylinder misfires just like this on a 2001 4.0 Jeep Wrangler with AT. Had a new aftermarket crankshaft position sensor, all the other things too, new plugs, new coil, checked all injectors for resistance, etc etc. Saw this video along with another one from Scanner Danner, both said to use the factory original Mopar part, so I took the chance, replaced the aftermarket crankshaft position sensor with the factory piece and problem solved! Thanks for posting the video! Great videos as always!
TL;DR: The old sensor put out a good square wave pattern but was inaccurate/inconsistent in ON time.
Thanks for the captures! I've never actually used a PicoScope before. I downloaded the software to look at your captures and gotta admit it's bloody cool. I was able to do measurements and analysis in about 5 minutes whereas it would have taken 20+ painstaking minutes with my Verus...
So you can't compare times between old and new. You're not running at the same RPM so times are irrelevant. You have to compare degrees of crankshaft rotation as that's the only thing that is constant. I measured the width of 4 pulses on the crank pattern on both the old and new waveforms. I used the same tooth every time to be consistent. On the old sensor I got 1.427*, 1.575*, 1.562* and 1.579*. On the new waveform I got 1.16*, 1.16*, 1.109* and 1.111*.
On the old sensor, each pulse lasted more degrees of crankshaft rotation than the new sensor. I imagine that's not what set the misfire. No two sensors are exactly the same so that would probably get processed by a crank relearn. HOWEVER... the pulses are pretty inconsistent on the old sensor whereas they are VERY consistent on the new sensor. The difference between the shortest pulse length and longest pulse length on the old sensor is 0.152 degrees. Even after going back through the new trace and looking at way more samples the largest difference I could find between pulse lengths was 0.011 degrees. That's going to be what's causing the reported misfire.
The time delay between when the tone wheel notch passes by the old sensor and when the sensor is able to fully turn on and off its transistor just is not consistent.
The Jeep obviously noticed your hat and you meant business...no frickin around
Will s And that's a REAL JEEP! Not one of those Fiat based monstrosities.
Lol... You won the comments..lol
I absolutely love this engine. I've had 3. Yes odd issues here and there but reliable and smooth regardless how many miles were on it. I took one to 356k, one to 375k and the last one was totalled in 2019 with just under 340k with a mint leather interior. Yes, that crankshaft sensor caused an issue on my 1997 Grand Cherokee TSi. Just stopped on me one day and I had no idea which direction to go. Luckily I had an uncle who worked at the Chrysler Jeep dealer in town and he helped me over the phone. I admit hearing those 6 cylinders firing up brings a tear to my eyes. Reminds me of years of worry free driving across the southeast. I drove one from 2000-2019 (2 1997 ZJ TSi and 1 2003 WJ Laredo). Always looking for a good one to keep a few years 1996-2004 only. Hope you and Mrs. O. had a good New Years Weekend. 🎉
This may surprise you Eric but your guesses are more often than not better the most mechanics or technicians knowledge today. Keep knocking out those cars and enjoy your days
Had a similar situation. Friend took his 4.0 Cherokee into the shop because of check engine light
at highway speeds. Shop said it was indicating all 6 cylinders were showing a "spark" miss and
they began replacing parts. ECM and Coil Pack and other parts to the tune of over
$2650.00 in parts My friend asked if I could check with the shop and so I called just casually
asked what waveform they were getting generated when they tested They said it was great and
had never showed a bad waveform and that was what throwing their troubleshooting off.
I quietly suggested that they might try changing the crankshaft sensor ( which they had not
done to this point. It is not my vehicle or my right to get into the middle of the problem).
Long story short, they changed the crank sensor and the wave forms returned to normal.
Sadly, of course they just added the cost of the crank sensor to the $2650.00 parts plus
labor bill telling my friend that somehow the "ECM had defaulted in it's code and caused other
parts such as the coil pack and crankshaft sensor to fail". I explained to my friend that such thing
just could not happen and if he wanted to dispute the charges I would be willing to help him but
he would need to start the process not me. He never did anything about it so he received
an education, I received an education and I am sure the shop received an education.
Aloha from Maui
Randy Gentry I guess malpractice insurance won the lottery that day🍾
So, what is the ethical way to run through this parts changing fusillade, short of bringing it to Eric "the Swami" @ SMA ? I got $9,899.00 hammers too, but feel bad using them.
That feeling us mechanics get when shit goes right
Sorry, "when shit goes right" is an alien terminology. Words that dont live together peacefully in my world. LIke oil and water in the crank case. :-)
Classic video. I had a grand Cherokee similar issue. It would run like crap while crossing railroad tracks. Bunch a shops couldn't figure it out. Customer brought it in, through a monitor on it and cranked it up. Went behind the truck and climbed on the ball mount and started jumping up and down. Jeep began running like crap. I said crank sensor. Took a long screwdriver and then tapped the sensor and again ran like crap. I feel better about your guesses than other peoples facts. ;)
One of my all time favorite vehicles of all time !!!
daniel w Cherokees are awesome!
Good job on getting a Mopar sensor. I had a 97 grand Cherokee 4.0 and I had a similar issue and I replaced the crank sensor with an aftermarket. It ran great for about a month then the same issue. I got a Mopar one and never had the issue again. I learned Jeep's are picky with sensors.
Sometimes the old EPG and your gut work well together. Another Victory!
Sooo "test then guess"? Now you'll have to change all those sma bumper stickers. Great vid, thanks Eric.
as always,sma comes through with a perfect repair,great job mr o.
This is what they call "an educated guess"!! Nothing wrong with that. Good work. I think this is a very good looking car, Been looking forone for a while here in Sweden. But hard to find in good shape. Good work, love your channel!
Just came in from rustling up the dear and laying some corn 🌽 and a new SMA. Good morning just doesn’t get any better than this on a Saturday.
Wow Never seen a Missfire On all 6 cylinders before And the Engine Run Smooth as Butter that is Interesting Defenitly looks like a Crank Sensor Failure good Video as Always Eric O great find on this video @SouthMainAutoRepairLLC
THANK YOU, THANK YOU, THANK YOU, Mr Polish Guy! Just fixed my Plymouth Neon with the same shit (money light, flashing, P0300) after replacing CKP, CMP, plugs, wires, Coils, fuel pump, fuel filter, PCM, O2s, PCV, Intake gasket, Injectors and many cuz words nothing. After watching this video I ordered a MOPAR CKP and problem SOLVED! Thanks again Eric O.
Had the same issue on my 2000 Grand Cherokee and replaced the same sensor with OEM and it fixed it that was 2 years ago
Ssshhhhhhh it was not a guess it was hypothesis, theory, prediction sorted!!!!!
bodgit and leggit garage a
A
It's so good to have a lift, It was a full-on pain in the royal ass for me to install that sensor..kind of reminded me of that old school board game operation.
I also had to undo the transfer case driveshaft.
So sorry for your loss,He must have been quite a father and teacher, rest in piece.
I cant believe I heard Eric O. Say that he was making an educated guess??? Lol. I could see the legitimate agony he was feeling by his facial expressions when he made that statement. BUT that's exactly the reason that people TRUST and APPRECIATE his candor about his work. There obviously was something wrong in the circuitry of that aftermarket sensor that was telling the ECM bogus information. I am surprised you couldnt test that old sensor once it was out of the jeep to see some form of bad communication coming from it in comparison to the new one. Not sure how to read digital communications so ill leave that up to the expert Eric O. I will say it was nice to see a video from a TH-camr's car as we like to give back to the SMA channel by provide good subjects for diagnostic videos. I hope more TH-camrs bring their car to Eric. He deserves the business.
I agree 100%!
Could have been something as simple as that tiny bit of noise causing the problems. Improper shielding in the aftermarket sensor? Who knows? Sometimes cars and trucks hate aftermarket parts and you'll hear a distinct "Patuewieeeeee..." sound as it spits it back out like a 1.5 year old eating his veggies.
I hate guessing myself. We want data to back up our claims. My theory is that the sensor it's self was on it's last legs internally (doorman maybe? or BWD) when it was put in and the coil inside is shorting it's self. Anyway awesome video as usual Eric. Keep it up!
Missing Misfire Mystery Solved?
Once again a great video and the fact that you were "guessing" doesn't worry anyone who know that your guesses are based on a
solid foundation of both knowledge and experience and you can guess on my car any day. By the way I noticed that when you start the video
and show the cam/crank relationship at idle the cam signals are lining up with the fourth crank signal but when you rev up the engine the
cam signal now is lining up on the third crank signal. This might explain why the misfire code are being generated. I notice that after the
crank sensor was replaced the cam signal stays with the fourth crank signal even at higher RPMs. Please check it out and let me know what you think.
Keep up the awesome videos they are teaching me alot and you crack me up with your terminology and the ease and enjoyment that you get when
working on cars. Thanks so much.
Having same issue with a 01 Jeep Wrangler at the shop. At 3K RPM shows ghost misfires. I put an aftermarket sensor and didn't help, guess ill go OEM. I noticed you didn't relearn the misfire counter when installing the new crank sensor. You can see and your scanner it says adaptive learned no. That's why it wasn't showing misfires. I know because when I changed the crank sensor it wasn't misfiring again until it learned the misfire monitor. You fixed it though since the vehicle never returned.
Good video Eric it pays to be honest that jeep is in nice shape and it looks clean again great video
Nice Quiet Riot reference.
It's the end of the world as we know it, but the jeep runs fine. Eric fixes it everytime....when in doubt, win the war. Eric for the win!
one of the greatest jeeps of all time
I know three retired Chrysler engineers who were very familiar with the JTEC PCM. While all generally praised it, the word around Auburn Hills was that JTEC was an abbreviation for "jus' tryin' to be an engine controller". I wouldn't be surprised to find a line of code someplace that checked for Brand X parts!
There used to be a video somewhere on YT that used waveforms etc to go deeply into the differences between OEM and aftermarket crank sensors on Jeeps. I can't find it any more, but I recall that they *did* pinpoint differences that could account for why Jeeps are so picky about them, and they weren't in any way obvious.
My 02 wrangler 4.0 had the same problem. Found out that the sensor has a felt pad on it you need to mash it into the flywheel and it wipes the felt off. The oem came with instalation instructions saying to do it, reinstalled the aftermarket one mashing it in and worked perfectly, couldn't find anything anywhere online to help.
I have seen this on multiple Cherokees. The first one had me banging my head against the wall trying to figure out the problem. Came to realize after that the truck originally did not start and the customer had brought it to a shop where an aftermarket sensor was installed. Long story short, my cam/crank waveform was obviously fine as was the crank pattern itself to my eyes. "Guessing" that the aftermarket sensor was the culprit, I changed it with a dealer part and problem was solved. Only thing I can think of is the air gap may be different between it and the aftermarket part. Other than that, I have no idea what else would cause this.
Modern electronics. Garbage in, garbage out. You sometimes have to make an "educated guess" to get the problem solved. Good job.
Even to the most casual observer the answer was apparent it was gyroscopic instability produced by a low center of gravity, or the knueter valve was clogged up :o) Way to SWAG the problem Eric
Eric O. You didn't guess your just that good . Thanks for video's keep them coming
That Jeep is mint!
Won't last long with Pennsylvania winters
Handled with the precision of a carpenter's eye-level, on: "The money!"
Hi Eric, very interesting case, I downloaded the waveforms and the only difference I could find was that the old sensor at idle and 2500 rpms the square signals from crank were longer time base wise idle= 697 us Old to idle= 472 us new at 2500 rpms old =216.9 us new= 133.3 us. Would that be enough to create false misfires counters?
Yeah the waveform plateau length seems to be the only difference
It would be easier perhaps if it was synced to the "missfiring cylinder" before and after
MrBorntoroll the thing here is that there was no actual misfires, so this is more of a software glitch than an actual misfire. All cylinders showed misfire only on software.
I mean with the firing event we would have some more measurments as the pcm measures speed of the crankshaft after cyllinder firing to flag a missfire.
Ok. We kinda have spark events. The theory: if PCM counts time of crank rotation after spark event not until every next HIGH hump but until next for ex "big low gap and HIGH hump" (to give time for combustion to occur) then we can see that with old sensor be get quite bigger (in ms) time delay which can be calculated as missfire if PCM wants to see shorter time. The bad news: the theory doesn't work during idle.
yes the millsec would make a differance, since no ditributor to turn then im guessing the random delay in the crank sensor is making the light come on :) great work as allways!
I had a similar symptom with a Honda accord. Misfire that got incrementally worse over a years time. Did all the checks, diagnosed it as a bad exhaust valve. Put a head on it (correct diagnosis, the exhaust valve had part of it eroded away in a neat little perfectly round pac man-esque bite). The similarity was when it was done it ran flawlessly. At RPM above 1000 it would flash the money light and set a misfire code, but it was running perfect (as a honda can). For 2 days it drove me nuts, had to walk away and do other payers as i contemplated this bizarre turn of events. The supervising super tech at the company did all the same tests i did, called tech support. No dice. I started exploring EVERY possible data parameter. As i stumbled through every possible menu in the scanner looking for ANYTHING that could help, i find an option buried in the engine side (Snap on scanner) "reset engine adaptives". CLICK!. THE PROBLEM WAS GONE. I was thinking it was something like that on Eric O's headache. First time i had ever seen that as a menu option.
Love your honesty. You gave us an educated guess. Better than I could do
I've heard from different sources that the aftermarket sensors have some kind of weirdo diode in them or something like that but in the process of heating and cooling this diode for the 5 volt reference ends up popping and it allows it to bleed through the reference wire essentially giving it 2 signals it's throws the computer out of wack but when you go to look at through the Pico you're seeing the direct line in and that's why you can't see a fault you're not seeing what's bleeding back to the computer if that makes any sense.. at least that's what was explained to me.... just an FYI for your information keep up the good work Mr.O
The Mopar Crank sensor using a specific code and pulse to communicate with the PCM (think of it like to encrypted phones taking to each other). The aftermarket ones are close but not enough to be registered 100% with the PCM. So there Crank sensor is saying "We're all good dawg" but the PCM is only recieving "We'r al d daw." Some are so off they won't even start even though the scope looks good.
Just wanted to add if you have to but aftermarket sensors the ones that will give you little to no trouble is Standard Motor Products. This goes for ALL MOPARS. A few of us guys on the forums fingered out why they didn't work when we were watching the programming in the PCM itself.
Gives you the right to wear that cap with a jeep in the shop lol .
cool to have a vid on a saturday too, have a day off tomorrow lol .
That looks like a real clean Cherokee!
From an electronics point of view, I can't find the specs for the picoscope, but I suspect that the aftermarket ckp is producing noise on the signal line that is too fast for the Pico to catch. Next time I get one of these in the shop I'm going to use a 200mHz scope on it and see what there is to see. Maybe it's nothing but, that sensor HAS to be producing something the ECM doesn't like. We just have to find it.
Parts cannon for the WIN! I blame it on the Chinesium ;)
farmboy30117 AVE! FTW. I think ScannerDanner has talked out aftermarket vs OEM sensors in the past.
Agreed. Back pickup. Inconsistent.
Just bought myself a parts cannon and am feelin good !
You don't have to buy them. They give them away for free at Autozone and Advance. The ammo for them can get expensive though.
Lol
You sir are freaking awesome. I just replaced a CPS on my daughters 4.0 jeep and I am trying to find a misfire in the engine.
I would pay top dollar for Eric's experience based guess any day.
sometimes my parts cannon needs a good re - load !! great vid, eric. thumbs up all the way
2001 GC with lots of pissy-little-'minor'-tooling-around-getting-it-right-things-that-annoy-me-so-it-doesn't-let-me-down-&-I-know-things-are-right-issues. They're not bad vehicles, just vehicles that need maintenance!
Liked & subscribed! TYVM for an informative channel.
O2 sensors are another red headed stepchild for these as well as clean battery terminals. I've seen on a few occasions these Jeeps are fussy about very clean voltage & copper core spark plugs. No better plugs for them.
These are the cars that don't play fair. Tests perfectly yet is bad. That's why it's nice knowing a few other techs that you can share cases with. Identifix can come in handy for these problems occasionally but between me and a buddy of mine one of us has usually run across these issues at some point.
Hi Eric. Downloaded the files @2500 rpm and used Pico measument tools. Old sensor duty cycle is 10,28% New is 11,1%. 7% difference in pulse width -> upto 25 degree variation to angle speed dRpm. Old sensor became more insensitive detecting a flywheel teeth. Turned on later and turned off a earlier. Could this be the diagnosis?
Janne Pohjala That’s what I found as well. The duty cycle obviously didn’t affect engine operation but the PCM was sensitive to it.
Awesome! I wonder if the magnet on the crank starter wheel gets weaker with time and heat, thus the heavier wound and more sensitive mopar sensor is the only one accurate enough?
Where are the files I looked for them couldn't find them
Thats what I thought. That maybe the aftermarket sensor is manufactured slightly differently that maybe the PCM wasn't getting the full value it was expecting.
That's a pretty clean Jeep Cherokee!
It needs 5 more "ignition tune ups" and about 11 bottles of fuel system cleaner, then keep telling the customer it's bad gas if he comes back.
most people say "i dont know" when asked when was the last time spark plugs were done (and on this....people forget the cap and rotor is a wear part)
so i usually will pull a plug to have a gander
.
but ya.... ive shotgunned my own cars ignition (dont have time, and dont want to WORK on my own shitboxes)
99 GM 3.1...... waste spark can go F it self
.
new plugs and wires.... still had a soft miss that the CEL didnt light for
but the old plugs WERE quite old, and the wires 10 years old....
.
turned out..... bad coil
then i tightened the bolt too much because it was -30f....
and cracked that coil
.
then i got a bad coil..... that split in half
turned my car into a 4 banger..... limped my way into work
.
and finally..... ive had NO issues for 80,000 miles
and now its about time to do the plugs again...
.
PS
on my 97 4.0 jeep..... i have a miss that cant be felt (some times cly 5, some times random multi, or sometimes 2 5 and random)
but its usually going down a hill, with like 2 gallons of gas in the tank....
.
throws the code with in 200 feet of the same hill.....
.
doesnt seem to do it (as often) when it has 1/4+ tank of gas
.
oh well..... its a mopar..... reset the code, keep driving till something changes / gets worse enough to fix
There are times when an "experience based" approach is necessary. I have worked on wind turbines when nothing was out of specs and everything was apparently good. But the turbine would just not come online. Dig back into my experience and I just knew that if I replaced part x, then it would come online.
Sometimes that is the only way to get it done. If it works, and the customer is happy, don't sweat it. You spend a ton of time of troubleshooting customer cars, and ensuring that you get the exact problem nailed down and fixed right. If there is an occasional time where you can swap a common part and get the car fixed and back on the road without spending two or three hours of shop time, all based on your experience, then so be it. You will get the car back to the customer faster and with a smaller repair bill, and you can get on to the next one.
It is the odd ball problems that really require your level of expertise in troubleshooting and attention to detail to iron out.
Ah, the venerable 4.0. Wonderful engine!
Eric O., in the know!
That Jeep is very clean
Loved this one, keep up the great Video
Good morning Eric!!