If you are a real tech you undestand how raw this video is ... The most thrilling part of this career is searching for the answer . Great video Paul , thank you for the service you provide to the automotive industry.
Totally glad to see this as I have seen this several times as well. One example exactly like this was a hydraulic lifter failure. If car sat a few hours the compression would be bad however crank long enough or run the engine and eventually oil pressure built it up. An in-cylinder pressure transducer while the issue was happening caught the issue and in fact even caught the issue correcting itself!
I think the best course of action there would be to let the car rest with the coolant system pressurized, then put a endoscope in the cylinders after a few hours depending how bad it is. Can rule out head gasket or oil intrusion.
I use to do this on early 2000's Nissan Sentra's whenever I saw a misfire fault that happened only on start up. It was so common to see a head gasket failure on these for some reason. It would be severe enough that you can see the coolant just by shinning a light in the cylinder w/ the spark plug removed.
Despite of issue not resolved, the approach and video is Great. Sometimes i went through same situation. This type of car improves your knowledge and research on problems and solutions.
No idea why you have that connected with money. I'd like to be more than 20 yrs. younger but it has nothing to do with money. Had money then, have it now. The older you get, the more years you wish you to take off.
I'm leaning towards a sticking valve. If the engine is shut off and that valve is held open, when everything cools down the guide contracts down on the stem just enough to hold it. Then after cranking a while or running, it expands and lets the valve move freely. Could be a pretty worn guide that doesn't scrape off any carbon buildup and drags some of the carbon up into the guide. If the valve cover isn't too hard to pop off, try turning the engine over by hand and see if any valve fails to close completely. I know you didn't get a chance to go back to it, just thinking out loud.
Smh must admit dig the equipment used, way advance for me as im sure it not cheap 60% of any automotive repair is tools had= difficulties/time to repair, cool to see high tech way of diagnosing this type of issue, your videos are very informative and teaching 👍
I had one of these SX4s come in a long time ago, was doing pretty much the same thing. Always had good relative compression though, but always missed at idle (can't remember codes) but ran 100% on the road. Customer only approved a hour, pistons looked good (no signs of wash) no leaks, not losing or blowing coolant according to the customer, sew lots and lots and lots of sludge under the oil cap. Best guess with what time we had with it was a lifter collapsing, did a oil change and told them to drive it. Never saw it again. Couldn't find lifters for it at the time anyway, so figured they weren't changing their oil to much.
Hey Paul! These are great videos in my opinion, as not all new techs would have that knowledge and experience as to when to ask for more time and how to explain there are situations where it can get expensive for the customer with out a fix and not everyone is prepared or willing to charge that kind of time
I've used brake clean / starting fluid and watch fuel trim to find vacume leaks . Also used oil samples to find trace amounts of fuel or glycol in oil.
yes my friend that is always a problem you look at one fault but if the car has multiple faults sometimes you have to address one so you can make a proper diagnosis of another because one can affect the other . bloody nightmare on a few old bangers i have looked at . as you say communication with the customer is key and your assessment and honesty is another . it’s going to cost that much to go further how much money do you want to invest in this car if it’s only worth this much dollar but the bill to fix it is more than the car is worth
Cause and Effect... I totally get why you took that path going after that fuel concern. If it was fuel Causing the Effect of washed cylinder = Low compression... Definitely made compete sense. 😎👍 Cheers Brother
I had a toyota camry 09, same symptoms but this was prior to me owning a lab scope so I can't share any detail on compression test with Amp clamp, but what I can tell you is the only way I found it was doing a manual compression test with a Guage with all spark plugs removed from the cylinders, when the plug/plugs were installed it was holding the compression in. If that makes sense 😅. It happened to be blown between cylinders so when let's say between cylinders 2 and 3, so when I had plug 3 in checking compression on cylinders 2 gave me good results. After removing both 2 and 3 let to low compression on both.
@@gibsonwill18 Yea, confirmed with leakage test with plug removed on both cylinders and found leaking out of the cylinder into the other cylinder. And cooling system never over pressurized either was very interesting.
What I think about when watching this video= 1960 to 1980 We used vacume gauges to read 1980 to 1996 we used in cylinder compression testers and smoke machines to read 1996 to today we use scopes to read The evolution of diagnostics testing and. Great video👍
you had two vacuum lines. PVC and distributer advance. you could still get to the plugs to read the compression. 2030 don't need scopes either since they will encrypt the signals so you can't tell what you are reading.
Great video Paul and Caleb. This is a good video on how to approach vehicle problems and not fire the parts cannon at it. No need to apologize for not having an update video on this car. I think your right about a valve or maybe a lifter issue but the only way is a visual of the valve train. This is just my opinion. God Bless.
Fuel wash could be eliminated quickly based off LTFT and lean DTC. That much fuel would cause the PCV system to draw fuel vapors from the crankcase and cause negative fuel trims. My bet is like you with valve train. My best guess would be a worn valve guide. It seemed to get better after the engine ran for a few minutes and things loosened up. I would repeat relative compression test with some first look sensors after a cold soak. I always enjoy your videos. Thanks Danner.
That’s a great video presentation for our learning experience / process of teaching us !!! It works out nicely to make us alert and focused ; discernment on using our own thinking 🤔 along with your thoughts & coaching & assistance . Thanks gentlemen ! 💥👌🏼🎯
I don't remember hearing about cam/lifter problem with your Power Wagon ( a killer cool rig by the way). Could you fill us in when you have time? Just an old retired guy here trying to stay in the loop with your ebook and videos. Many thanks for all you, Caleb and your brother do for us.
Hey Danner! My understanding is that a misfire, even from over fuelling, will show up as a lean condition. The reason for this is there is the same amount of oxygen entering the cylinder as usual, but with less of that oxygen being converted to co, and co2 through combustion. Therefore the O2 sensor reads lean exhaust and jacks the fuel trim numbers up. After all it is an oxygen sensor, not a fuel sensor!
You’d be correct, but also take into account that when he was getting the fuel trim readings, it no longer had a weak cylinder. And here’s where I’m just wondering out loud - if the misfire isn’t caused by weak spark, wouldn’t the fuel still be ignited? Then it would it necessarily still show up as lean to the O2 sensor? In other words, I can see how the O2 would absolutely register lean on an ignition-related misfire, but is it always true that weak compression will cause an incomplete burn?
There are variables to what you're describing. It was not misfiring completely. If overfuelling was causing a dead misfire, you'd be correct (somewhat). Fuel absolutely does have an affect on how an oxygen sensor produces voltage. Yes, it is an oxygen sensor, but fuel plays a factor. To prove my point. Watch your fuel trims and disable spark, then watch your fuel trims and disable the injector. (Make sure the injector is still firing when you disable spark) Fuel trim numbers will be less positive with the ignition misfire. Why? People call this the "tomato sensor" lol (is it a fruit or a vegetable) www.scannerdanner.com/scannerdanner-premium-chapters/chapter-1-universal-testing-methods/chapter-1-universal-testing-methods-full/199-operation-of-an-oxygen-sensor-part-1-pg-4-expanded-content.html
@@ScannerDanner thanks for the reply Paul! I’ve got your book, but I’ve been considering premium for a while. Think I’m going to pull the trigger on it.
Just had a vehicle with the same intermittent issue.compression keep coming and going. No fault codes at times. narrowed it down to carbon build up on intake valve. Injectors were serviced. GDI engine
This got sideways early on, and when that happened I thought, "I would stop here and get more history/background from the customer". However not so easy for you since you are not the direct point of contact with the customer. That got me thinking to myself boy he is between a rock and hard place with no history, and how often that must happen to you given you are almost always a 3rd party diagnosis. At the end of the video I was relieved to hear your thought process was the same about needing more history. Just from talking with the customer IE "Oh yes it only misses when it's cold, or only when I first start it", "yes I do have to add small amounts of coolant every few days" for example could give so much guidance on where to look next.
I had a cyl #1 intermittent comp concern just like this on a VW Cc R Line. It baffled me for a while. I barely managed to sneak a bore scope through the oil fill and found a broken intake valve spring.
Aren’t you glad you didn’t drop by to check it when it was warmed up. You would have been chasing a different problem. Good conclusion at the end. Compression problem and lean problem most likely two separate problems. Either way he was looking at an internal engine fault that may have been expensive just to get to the bottom of before replacing any parts. Thanks for mentioning the new coils and plugs were a waste of dollars. Absolutely no diagnostic time to decide that. Just SWAG (Scientific Wild A$$ Guess) Appreciate your efforts. I’m retired after fifty years in this business. You can get behind very fast too.
In my experience attending Suzuki's ........... usually very reliable, most common issues ...... Plugs and coils usually thru neglected servicing and most common faulty 02 sensors causing a P0420 code.
Metal expands with heat ,when its cold ,it might have given you different readings than when its hot .expanded pistons and rings might have sealed the cylinder .when the engine is cold take a compression and leak down test if those two tests are favorable then you might have a bad lifter,thats my take,good job tho.
Way to clean the video up at the end and clear everything up!!! On the surface it might not look like a person could learn anything from this case study,,,, However there is knowledge to be found.... As the old saying goes, every time you pick up a basketball and dribble it you will get better!!! ( I have to dribble with a youth size basketball because my hands are not super big. People honk their horns all the time when I'm out dribbling a basketball because I'm so skilled at it, both right & left handed.
Man thank you for this vid but thanks for the key fob programming video on your premium channel it's right when I needed it my key quit working and I lost the key of the loaner car i was driving ❤😂
Had something similar on my own car once, valve seat had worn as the valve rotated when running it would not seat correctly at a certain point but then cleared shortly after
Paul, Would pressurizing the cooling system, putting a camera in #3 and looking for a head gasket drip when cold be a possibility? It ran like crap cold then went away... Thanks for the content.
No, that is false. Ford COP coils and the PCM drivers for them are garbage in some models. Disconnecting a coil will not damage anything. Even if you did generate a voltage spike it would be nowhere near the 400v spike the primary circuit already creates.
A leaking injector is putting too much fuel into a cylinder and the negative trims are the ECM taking fuel away (reducing injector on-time from the base line map)
@@ScannerDanner Thanks for the reply! I was thinking about it in the sense of cylinder wash giving a misfire. which in my mind would give positive fuel trims because of the miss. Always learning! Love the Videos!
Lots of comments related to lifters. Maybe one is sticky when cold, then loosens up as it warms up? If you were able to go down that rabbithole, how would you test it?
Step 1 would be to ID the exact cylinder that was dropping compression. Step 2 would have been an in-cylinder psi transducer in that cylinder and then aquire some waveforms.
@@timothyball3144 Just to add to your questions....as he stated you would want to do an incyl capture to yes "see" if there is a valvetrain issue. If a lifter was the issue you would see in the incyl psi trace that the pressure change at certain points would look drastically different then the known good cylinders, in particular the points that are directly related to opening and closing the valve. If it was a leaking valve you would look more for a leaning compression tower and deep exhaust pocket. In short, yes there are methods to narrow down the root causes of compression loss with capturing waveforms, hope that helps some.
@DTEAuto Thank you. I'm sure that for those who are familiar with what waveforms say, it would be obvious. Me? For the kind of work that I do, a scope might be useful once a year or two, so realistically, learning that kind of stuff isn't worth it for me. Just knowing that it's possible is good enough.
I am HALF WAY through the video. I have seen this on broken valve springs, and i have seen "lifter" issues (i use the term lifter loosely, can be an auto adjuster in a rocker or a hydraulic follower.) Once properly pumped up, it works. Lets see. If its coolant or another fluid, it would likely cause a compression increase in the cylinder on initial cranking. What does the oil smell like? Every diagnostic has the chance to way down the rabbit hole.
Any scope is better than no scope! What's your budget and what type of testing do you want to be able to do? There are single channel scopes out there that are very capable. It's call a uScope and the master kit is around $400 www.aeswave.com/scannerdanner I'm using it in my latest video th-cam.com/video/fCfqGKw6EMg/w-d-xo.htmlsi=6JY7uk8kqXSO72p5
"i need a better history on this" that is a conundrum. its nice to have but not always available. and it being intermittant......... this would have been a fantastic case study had it been available to finition.
Hi Paul, that definetly sounded like it had a low compression to start with, so i dont think it would be anything else, wonder if it had a sticking valve or broken valve spring or somethng...weird...F.
Long long ago in another world probably around 1980 I had an import I think was a Datsun 240Z that missed at startup and quit after a slight warm up. It also had the misstep in it's cadence. It turned out to be a loose spark plug. It wasn't coil over plug so I could hear the compression loss hissing while running until partial warm up. My theory is it was just loose enough and tightened up when heated. Not sure but that was my theory. I never saw another one since.
This is interesting. I'm going after a similar issue on my 05 Cavalier 2.2 with 313,000 miles 1 owner , car came from my gf parent's I saved from them hauling off cause the car was old and has high miles but that never bothers me . Anyways It all started doing this random cylinder 1 misfire and then it turned into multiple cylinder misfire codes and I had just got the car at this time when it first started this problem and I figured it may need plugs and sure enough it did and after I did those it seemed good as new and it made a 4 hour trip home but however.... it came back some many miles later and had a dead misfire on cyl 1 so I went to junkyard to save money and grabbed all 4 fuel injectors off a car that just came in that was wrecked same year popped those in and bam she fixed until now we're at 318,000 and it's doing this random stuff again!!! And now it will cut up and misfire at idle or it did this thing where it wanted to cut out soon as u punched the gas from a dead stop or even just granny speed take off like the TPS had a dead spot in it . But once u got past that part the car had all of its power and no issues at all then driven along at 55 or whatever and car did this jolt like a transmission jerk and I knew it was the engine side causing this .
Getting to the point here trying to not waste your time . I checked about these cars on line and everyone and everything points to the ICM so I'm like ok... then so I checked it and the pins had green corrosion on them and so did the coil pack side to so I ended up replaceing both parts and everything was way better this time till..... 200+ some miles later in that range the code came back for multiple cylinder misfire and so did the cut up with the gas pedal and the misfire at idle did too . I did a compression test and that was not great however it's not to terrible that it should not make it do this and then not again unless it's sticking valves which could be and I am thinking of running seafoam down the thrttole body and let it chew on that a bit to clean carbon out and see what that does to it . Compression readings Cyl 1 115psi Cyl 2 135psi Cyl 3 145psi Cyl 4 120psi Like I say it's not good I know but it's not to terrible enough that i would think it would do this random problem unless it's a sticking valve or maybe the injectors I used but it's hard to say
One more thing I wanted to add was that when it misfire again and code came back I parked the car for a few days and then i went back to start&drive it and bam it was all gone and back to normal again but the light is still on so it's really odd . Gonna try seafoam I've used it on so many cars that ran like crap and it helped and fixed the problems . I always stick to same place or places to get gas I'm very particular
My car working properly and I do not feel anything bad. No check engine light and no other errors. LFT is 4% right now. But when I check OBD Mode #6 data for misfire, there every cylinder shows some misfires like between 0 to 30. My question is that is normal with every car or my car must have some problem and there must no be a single misfire?
Any reason you were checking Mode 6 data to begin with? How are the misfires listed? Is there a threshold of min and max? I wouldn't worry about it at all. Could be the scan tool you're using 🤔
You did the easy tests first and learned enough about the car to get yourself out from under it in an ethical way. Why do a bunch of other tests when the customer is already done with the car? I do this with customer's audio gear all the time and my boss hates it but he makes more money with it. Go figure. When you run a business it seems you lose your mind.
so when we have an injector leak or a head gasket problem or a valve problem, the f trims will be very negative at idle but at the highest revs they will become normal?
@@ScannerDanner I want to ask a question because I'm trying to make a strategy with the f trims in a road test, I know that pcv egr purge valve leaking injector or leaking valves gives negative f trims ritch condition at idle but at high revs won't the f trims become normal?
I don't know Dan. I just fought a similar problem same symptoms. As the cylinder temp warms up the seat expands and it kind of reseats itself. That kind of explains the obvious intermittent compression loss you proved out. Then seemed like nothing wrong. Love your channel. I learn something new all the time. Irregardless the head is likely coming off for this problem. Could also be head gasket between #2 and #3. and sealing itself up when it warms up a bit.
Oh also, that was back in 97 on a quad 4 in a 90 Olds calais 442. LOL Also saw it on a couple SB Chevy engines. Finally figured it out with a cylinder leak down test on all of them.
Brother to be honest and from my perspective what I see in this video is what can happen to technician in real life, looking to fix one thing find another issue
Could be a mechanical failure on an injector no circuit code because electrically fine. My bet is an injector mechanically done. Now not did you not find the evap leak but now you’re thirsty haha
ejector? You mean injector? And no an injector does not cause low compression unless is was spraying fuel all the time causing cylinder wash, which I proved was not the case when I looked at fuel trim
What's the point of this starter test when you can pull the plugs and do a compression test in 10 minutes. You're pulling the plugs anyway to check the plugs for oil, coolant or fuel wetness and to do a leakdown test.
On this engine sure. What about a V type engine where the intake covers half the cylinders? So many examples I can give you where this is THE test to start with. Just crank it over and listen first. 🤔
Well sure, on an engine where you might have to remove the intake for a compression test, it would be quicker, but I'm talking about THIS car where the plugs are right in front of you.
I didn't say that. If this was meant to be a learning demonstration, great. Just that in real life situations, the quicker more direct method is usually more productive.
@@atikovi1 maybe you're new here, so that makes sense. My entire channel and every single case study I show is aimed at my students. I'm a technical trainer and have been for over 20 years. Thanks!
Actually I thought the diagnostic process was clear. You did start with what appeared to be a low compression cylinder that went away.. Hooking up the scanner demonstrated that you had the opposite problem with Positive fuel trim numbers as opposed to negative fuel trim which should have been the case with a leaking injector which may have have caused low compression. In my mind you made it clear that you were shifting from looking for the cause of the low compression which had cured itself for the moment to looking for the cause of the positive fuel trim. Totally unrelated. You were verbalizing what you were doing very well and I followed the process without getting the two issues confused. Just sayin'. The low compression cause has got to be tough to diagnose when it disappears. Seems like it would require a tear down and careful inspection of all the parts involved. Perhaps not worth it to the customer.
Dear Dan, Why do you seem to show up with videos where you're severely lacking essentials tools? It's not an "every time!" thing, but definitely an "often" kinda thing. Maybe it's my perception...maybe it's Russia. Probably Russia. I dunno. Appreciate ya nonetheless - Cheers!
![Toyota Camry - Intermittent No Start, Backfiring, Runs Good When it Starts [Part 1]](http://i.ytimg.com/vi/Tro9M12LoQw/mqdefault.jpg)
If you are a real tech you undestand how raw this video is ... The most thrilling part of this career is searching for the answer . Great video Paul , thank you for the service you provide to the automotive industry.
Totally glad to see this as I have seen this several times as well. One example exactly like this was a hydraulic lifter failure. If car sat a few hours the compression would be bad however crank long enough or run the engine and eventually oil pressure built it up. An in-cylinder pressure transducer while the issue was happening caught the issue and in fact even caught the issue correcting itself!
Great to see you TH-camrs watching each other’s stuff.
I think the best course of action there would be to let the car rest with the coolant system pressurized, then put a endoscope in the cylinders after a few hours depending how bad it is. Can rule out head gasket or oil intrusion.
I use to do this on early 2000's Nissan Sentra's whenever I saw a misfire fault that happened only on start up. It was so common to see a head gasket failure on these for some reason. It would be severe enough that you can see the coolant just by shinning a light in the cylinder w/ the spark plug removed.
If its a intermittent lost of compression forget about head gasket.
yep ! good critique. thanks for re-emphasizing this !
First time viewer. Great job. Love the fact that you couldnt find the problem and admitted you needed more investigation. Keep up the good work.
Like you said initially we should have pulled the diagnostic trouble code first.. I appreciate your knowledge and diagnostics tips
Despite of issue not resolved, the approach and video is Great. Sometimes i went through same situation. This type of car improves your knowledge and research on problems and solutions.
Even if no clear smoking gun (?), I am relistening to all the pearls of wisdom. 👍
How i wish i was 20yrs younger...... The money to be made. Sweet video.
No idea why you have that connected with money. I'd like to be more than 20 yrs. younger but it has nothing to do with money. Had money then, have it now. The older you get, the more years you wish you to take off.
I'm leaning towards a sticking valve. If the engine is shut off and that valve is held open, when everything cools down the guide contracts down on the stem just enough to hold it. Then after cranking a while or running, it expands and lets the valve move freely. Could be a pretty worn guide that doesn't scrape off any carbon buildup and drags some of the carbon up into the guide. If the valve cover isn't too hard to pop off, try turning the engine over by hand and see if any valve fails to close completely. I know you didn't get a chance to go back to it, just thinking out loud.
Smh must admit dig the equipment used, way advance for me as im sure it not cheap 60% of any automotive repair is tools had= difficulties/time to repair, cool to see high tech way of diagnosing this type of issue, your videos are very informative and teaching 👍
I had one of these SX4s come in a long time ago, was doing pretty much the same thing. Always had good relative compression though, but always missed at idle (can't remember codes) but ran 100% on the road. Customer only approved a hour, pistons looked good (no signs of wash) no leaks, not losing or blowing coolant according to the customer, sew lots and lots and lots of sludge under the oil cap. Best guess with what time we had with it was a lifter collapsing, did a oil change and told them to drive it. Never saw it again. Couldn't find lifters for it at the time anyway, so figured they weren't changing their oil to much.
Hey Paul! These are great videos in my opinion, as not all new techs would have that knowledge and experience as to when to ask for more time and how to explain there are situations where it can get expensive for the customer with out a fix and not everyone is prepared or willing to charge that kind of time
I've used brake clean / starting fluid and watch fuel trim to find vacume leaks . Also used oil samples to find trace amounts of fuel or glycol in oil.
Me too, until an intake backfire ignited the entire engine compartment while a customer watched lol
yes my friend that is always a problem you look at one fault but if the car has multiple faults sometimes you have to address one so you can make a proper diagnosis of another because one can affect the other . bloody nightmare on a few old bangers i have looked at . as you say communication with the customer is key and your assessment and honesty is another . it’s going to cost that much to go further how much money do you want to invest in this car if it’s only worth this much dollar but the bill to fix it is more than the car is worth
Cause and Effect... I totally get why you took that path going after that fuel concern. If it was fuel Causing the Effect of washed cylinder = Low compression... Definitely made compete sense. 😎👍
Cheers Brother
Caleb/Paul,
Great video, explanation, and follow up - thank you.
Paul (in MA)
I had a toyota camry 09, same symptoms but this was prior to me owning a lab scope so I can't share any detail on compression test with Amp clamp, but what I can tell you is the only way I found it was doing a manual compression test with a Guage with all spark plugs removed from the cylinders, when the plug/plugs were installed it was holding the compression in. If that makes sense 😅.
It happened to be blown between cylinders so when let's say between cylinders 2 and 3, so when I had plug 3 in checking compression on cylinders 2 gave me good results. After removing both 2 and 3 let to low compression on both.
So what was it? Head gasket between the cylinders?
@@gibsonwill18 Yea, confirmed with leakage test with plug removed on both cylinders and found leaking out of the cylinder into the other cylinder. And cooling system never over pressurized either was very interesting.
What I think about when watching this video= 1960 to 1980
We used vacume gauges to read
1980 to 1996 we used in cylinder compression testers and smoke machines to read
1996 to today we use scopes to read
The evolution of diagnostics testing and. Great video👍
Problem is we still need the old school stuff for the mechanical side of the engine as opposed to the electrical and sensor side
@@pitchforkpeasant6219
Exactly 👍
you had two vacuum lines. PVC and distributer advance.
you could still get to the plugs to read the compression.
2030 don't need scopes either since they will encrypt the signals so you can't tell what you are reading.
Great video Paul and Caleb. This is a good video on how to approach vehicle problems and not fire the parts cannon at it. No need to apologize for not having an update video on this car. I think your right about a valve or maybe a lifter issue but the only way is a visual of the valve train. This is just my opinion. God Bless.
The best to learn from! Love your videos.
Fuel wash could be eliminated quickly based off LTFT and lean DTC. That much fuel would cause the PCV system to draw fuel vapors from the crankcase and cause negative fuel trims.
My bet is like you with valve train. My best guess would be a worn valve guide. It seemed to get better after the engine ran for a few minutes and things loosened up. I would repeat relative compression test with some first look sensors after a cold soak.
I always enjoy your videos. Thanks Danner.
worn valve guide would introduce a lot of white smoke at the exhaust
That’s a great video presentation for our learning experience / process of teaching us !!! It works out nicely to make us alert and focused ; discernment on using our own thinking 🤔 along with your thoughts & coaching & assistance . Thanks gentlemen ! 💥👌🏼🎯
I don't remember hearing about cam/lifter problem with your Power Wagon ( a killer cool rig by the way). Could you fill us in when you have time? Just an old retired guy here trying to stay in the loop with your ebook and videos. Many thanks for all you, Caleb and your brother do for us.
I'm not sure I posted anything here yet, but I did a bunch of short clips on my Facebook page. I'll have something here soon
Thanks Paul ! @@ScannerDanner
Nice diag Paul and great final explanation.
Brilliant stuff SD, very interesting, thank you.
Hey Danner! My understanding is that a misfire, even from over fuelling, will show up as a lean condition. The reason for this is there is the same amount of oxygen entering the cylinder as usual, but with less of that oxygen being converted to co, and co2 through combustion. Therefore the O2 sensor reads lean exhaust and jacks the fuel trim numbers up. After all it is an oxygen sensor, not a fuel sensor!
You’d be correct, but also take into account that when he was getting the fuel trim readings, it no longer had a weak cylinder.
And here’s where I’m just wondering out loud - if the misfire isn’t caused by weak spark, wouldn’t the fuel still be ignited? Then it would it necessarily still show up as lean to the O2 sensor?
In other words, I can see how the O2 would absolutely register lean on an ignition-related misfire, but is it always true that weak compression will cause an incomplete burn?
There are variables to what you're describing. It was not misfiring completely. If overfuelling was causing a dead misfire, you'd be correct (somewhat).
Fuel absolutely does have an affect on how an oxygen sensor produces voltage. Yes, it is an oxygen sensor, but fuel plays a factor.
To prove my point. Watch your fuel trims and disable spark, then watch your fuel trims and disable the injector.
(Make sure the injector is still firing when you disable spark)
Fuel trim numbers will be less positive with the ignition misfire. Why?
People call this the "tomato sensor" lol (is it a fruit or a vegetable)
www.scannerdanner.com/scannerdanner-premium-chapters/chapter-1-universal-testing-methods/chapter-1-universal-testing-methods-full/199-operation-of-an-oxygen-sensor-part-1-pg-4-expanded-content.html
@@ScannerDanner thanks for the reply Paul! I’ve got your book, but I’ve been considering premium for a while. Think I’m going to pull the trigger on it.
@@Code325looking forward to your comments on that lecture!
Just had a vehicle with the same intermittent issue.compression keep coming and going. No fault codes at times. narrowed it down to carbon build up on intake valve. Injectors were serviced. GDI engine
This got sideways early on, and when that happened I thought, "I would stop here and get more history/background from the customer". However not so easy for you since you are not the direct point of contact with the customer. That got me thinking to myself boy he is between a rock and hard place with no history, and how often that must happen to you given you are almost always a 3rd party diagnosis. At the end of the video I was relieved to hear your thought process was the same about needing more history. Just from talking with the customer IE "Oh yes it only misses when it's cold, or only when I first start it", "yes I do have to add small amounts of coolant every few days" for example could give so much guidance on where to look next.
100%! Thank you my friend
I think a pretty good take away for this is to always grab a ignition sync when you grab a RC capture.
I had a cyl #1 intermittent comp concern just like this on a VW Cc R Line. It baffled me for a while. I barely managed to sneak a bore scope through the oil fill and found a broken intake valve spring.
That quick, "clear flood compression test" really is a doozy!!
Your comment made me make a short this morning 🙂 thank you
@@ScannerDanner No, thank YOU!
Every time I hear those nice, even cranks, I thank the heavens that at least 50% of my engine is nice and healthy!
Love it😍
Thanks for sharing SD👍🏻
Special Thanks to cameraman Caleb😎
Please do some case studies with James Danner😍
Stay Blessed Guy's🙏🏻
I like it when you go to shops fixing cars, you're like boogeyman of mechanics 😄
Mr Danner you teach we learn
Aren’t you glad you didn’t drop by to check it when it was warmed up. You would have been chasing a different problem.
Good conclusion at the end. Compression problem and lean problem most likely two separate problems.
Either way he was looking at an internal engine fault that may have been expensive just to get to the bottom of before replacing any parts.
Thanks for mentioning the new coils and plugs were a waste of dollars. Absolutely no diagnostic time to decide that. Just SWAG (Scientific Wild A$$ Guess)
Appreciate your efforts. I’m retired after fifty years in this business. You can get behind very fast too.
In my experience attending Suzuki's ........... usually very reliable, most common issues ...... Plugs and coils usually thru neglected servicing and most common faulty 02 sensors causing a P0420 code.
Metal expands with heat ,when its cold ,it might have given you different readings than when its hot .expanded pistons and rings might have sealed the cylinder .when the engine is cold take a compression and leak down test if those two tests are favorable then you might have a bad lifter,thats my take,good job tho.
😎 SCANNER DANNER😎
THE GOD OF TROUBLESHOOTING
Thank you for the video Paul.
Way to clean the video up at the end and clear everything up!!! On the surface it might not look like a person could learn anything from this case study,,,, However there is knowledge to be found.... As the old saying goes, every time you pick up a basketball and dribble it you will get better!!! ( I have to dribble with a youth size basketball because my hands are not super big. People honk their horns all the time when I'm out dribbling a basketball because I'm so skilled at it, both right & left handed.
Man thank you for this vid but thanks for the key fob programming video on your premium channel it's right when I needed it my key quit working and I lost the key of the loaner car i was driving ❤😂
I'm really glad to hear that! Perfect. Thank you for your support too!
Right time to break out the old school compression gauge
I’m having this problem on cylinder 2 on my 2011 Subaru Forester.
Had something similar on my own car once, valve seat had worn as the valve rotated when running it would not seat correctly at a certain point but then cleared shortly after
It's Possessed ! I Love those :) Thanks for the Video.
Paul, Would pressurizing the cooling system, putting a camera in #3 and looking for a head gasket drip when cold be a possibility? It ran like crap cold then went away... Thanks for the content.
Love the pool cue stick
Great video
Hi Mr Paul Danner,Sorry to bother you. I just wonder if you still have your diagnostic’s book on sale,because I’l like to get it.Tanks
Yes sir. It is available on my website at www.scannerdanner.com
Thank you!
Piston ring might just be "kinda stuck" and get better when it warms up and thy expand a little
A leak down test would figure out that problem pretty quickly.
Agree
I would set vacuum leaks, and lean condition aside, and concentrate on intermittent compression.
Blessings 🙏🙏
My thought exactly as well.
good info, thank you for this video.
Question question.. some vehicles will fry pcm if u disconnect coil with engine running right? Scared me when u did that. I know ford states no go
No, that is false. Ford COP coils and the PCM drivers for them are garbage in some models. Disconnecting a coil will not damage anything. Even if you did generate a voltage spike it would be nowhere near the 400v spike the primary circuit already creates.
Great video, thank you.
Anyone able to explain how a leaking injector will cause negative fuel trims? Thanks!
A leaking injector is putting too much fuel into a cylinder and the negative trims are the ECM taking fuel away (reducing injector on-time from the base line map)
@@ScannerDanner Thanks for the reply! I was thinking about it in the sense of cylinder wash giving a misfire. which in my mind would give positive fuel trims because of the miss.
Always learning!
Love the Videos!
@@yvanauchterloni5923 oh okay, got it! In this case we have a no com with the ECM so we can't use any of that info. Good thinking though!
Excellent video
Thanks Danner
Hi Paul, could be restricted injector for the lean condition and for the compression issue sticky lifter maybe
It could also have been a valve issue causing the lean condition (misfiring causes false lean conditions)
But I agree with you too
Lots of comments related to lifters. Maybe one is sticky when cold, then loosens up as it warms up?
If you were able to go down that rabbithole, how would you test it?
Step 1 would be to ID the exact cylinder that was dropping compression. Step 2 would have been an in-cylinder psi transducer in that cylinder and then aquire some waveforms.
@@ScannerDanner OK. I see that, but I don't see how that would prove a sticky lifter. Or is it something that you would see in the waveforms?
@@timothyball3144 Just to add to your questions....as he stated you would want to do an incyl capture to yes "see" if there is a valvetrain issue. If a lifter was the issue you would see in the incyl psi trace that the pressure change at certain points would look drastically different then the known good cylinders, in particular the points that are directly related to opening and closing the valve. If it was a leaking valve you would look more for a leaning compression tower and deep exhaust pocket. In short, yes there are methods to narrow down the root causes of compression loss with capturing waveforms, hope that helps some.
@DTEAuto Thank you. I'm sure that for those who are familiar with what waveforms say, it would be obvious. Me? For the kind of work that I do, a scope might be useful once a year or two, so realistically, learning that kind of stuff isn't worth it for me. Just knowing that it's possible is good enough.
I am HALF WAY through the video. I have seen this on broken valve springs, and i have seen "lifter" issues (i use the term lifter loosely, can be an auto adjuster in a rocker or a hydraulic follower.) Once properly pumped up, it works. Lets see. If its coolant or another fluid, it would likely cause a compression increase in the cylinder on initial cranking. What does the oil smell like? Every diagnostic has the chance to way down the rabbit hole.
Awesome
Two words. Oillevel and hydrolifters
What scope do you recommend that I buy ?
Any scope is better than no scope! What's your budget and what type of testing do you want to be able to do? There are single channel scopes out there that are very capable. It's call a uScope and the master kit is around $400
www.aeswave.com/scannerdanner
I'm using it in my latest video
th-cam.com/video/fCfqGKw6EMg/w-d-xo.htmlsi=6JY7uk8kqXSO72p5
😊 👍
Good video and obviously a intermittent compression problem, very interesting. Are you still doing diagnostic work at your brothers shop?
Yes
Given more time could you have found the issue? Yes
Is it always worth it? No
That car unfortunately is headed for the salvage yard
Perfect...!!! 👌
The valves may need to be adjusted. This engine has shims.
"i need a better history on this" that is a conundrum. its nice to have but not always available. and it being intermittant......... this would have been a fantastic case study had it been available to finition.
Hi Paul, that definetly sounded like it had a low compression to start with, so i dont think it would be anything else, wonder if it had a sticking valve or broken valve spring or somethng...weird...F.
I would have liked to see under the valve cover to see if oil flow is constant on all oil ports
Wouldn't the sound be similar to a motor that was geting fuel injected but not ignited consistently, causing compression change from unburned gasoline
Yes, cylinder wash is a real concern and is a variable indeed BUT there are other symptoms associated with injector problems as well
Long long ago in another world probably around 1980 I had an import I think was a Datsun 240Z that missed at startup and quit after a slight warm up. It also had the misstep in it's cadence. It turned out to be a loose spark plug. It wasn't coil over plug so I could hear the compression loss hissing while running until partial warm up. My theory is it was just loose enough and tightened up when heated. Not sure but that was my theory. I never saw another one since.
That's a good reminder right there!
Hehe. I call that starting sound a "system seven"... Why? Say sytem seven, system seven, system seven,.... ;-)
Hydraulic Bucket lifter.
Dirty injectors will lead to high fuel trim, maybe it is the cause.
more importantly here is the intermittent compression issue
Tappets?
Possibly a loose valve seat which tightens with heat.
Cool case, do you what happened with the car after all?
No
Remember the old addage, never leave home without them . 😢
This car was not on my list of tools this day. We were simply there to check for a head gasket issue on my sons Jeep, that was it
Does that engine have variable valve timing or similar?
Not sure, we didn't get in it any deeper
Momma would have patched them jeans 😁
Hydraulic lifters.
This is interesting. I'm going after a similar issue on my 05 Cavalier 2.2 with 313,000 miles 1 owner , car came from my gf parent's I saved from them hauling off cause the car was old and has high miles but that never bothers me .
Anyways It all started doing this random cylinder 1 misfire and then it turned into multiple cylinder misfire codes and I had just got the car at this time when it first started this problem and I figured it may need plugs and sure enough it did and after I did those it seemed good as new and it made a 4 hour trip home but however.... it came back some many miles later and had a dead misfire on cyl 1 so I went to junkyard to save money and grabbed all 4 fuel injectors off a car that just came in that was wrecked same year popped those in and bam she fixed until now we're at 318,000 and it's doing this random stuff again!!! And now it will cut up and misfire at idle or it did this thing where it wanted to cut out soon as u punched the gas from a dead stop or even just granny speed take off like the TPS had a dead spot in it . But once u got past that part the car had all of its power and no issues at all then driven along at 55 or whatever and car did this jolt like a transmission jerk and I knew it was the engine side causing this .
Getting to the point here trying to not waste your time . I checked about these cars on line and everyone and everything points to the ICM so I'm like ok... then so I checked it and the pins had green corrosion on them and so did the coil pack side to so I ended up replaceing both parts and everything was way better this time till..... 200+ some miles later in that range the code came back for multiple cylinder misfire and so did the cut up with the gas pedal and the misfire at idle did too .
I did a compression test and that was not great however it's not to terrible that it should not make it do this and then not again unless it's sticking valves which could be and I am thinking of running seafoam down the thrttole body and let it chew on that a bit to clean carbon out and see what that does to it .
Compression readings
Cyl 1 115psi
Cyl 2 135psi
Cyl 3 145psi
Cyl 4 120psi
Like I say it's not good I know but it's not to terrible enough that i would think it would do this random problem unless it's a sticking valve or maybe the injectors I used but it's hard to say
One more thing I wanted to add was that when it misfire again and code came back I parked the car for a few days and then i went back to start&drive it and bam it was all gone and back to normal again but the light is still on so it's really odd . Gonna try seafoam I've used it on so many cars that ran like crap and it helped and fixed the problems . I always stick to same place or places to get gas I'm very particular
Step 1 (as these early GMs are known for shorted injector windings)
Measure the resistance of all of your injectors and report your readings
My car working properly and I do not feel anything bad. No check engine light and no other errors. LFT is 4% right now. But when I check OBD Mode #6 data for misfire, there every cylinder shows some misfires like between 0 to 30. My question is that is normal with every car or my car must have some problem and there must no be a single misfire?
Any reason you were checking Mode 6 data to begin with?
How are the misfires listed? Is there a threshold of min and max?
I wouldn't worry about it at all. Could be the scan tool you're using 🤔
You did the easy tests first and learned enough about the car to get yourself out from under it in an ethical way.
Why do a bunch of other tests when the customer is already done with the car? I do this with customer's audio gear all the time and my boss hates it but he makes more money with it. Go figure. When you run a business it seems you lose your mind.
Is this the same one from time long ago? Believe electrical issue diag.
First time seeing this particular car
so when we have an injector leak or a head gasket problem or a valve problem, the f trims will be very negative at idle but at the highest revs they will become normal?
Valve issues can go both ways. What we were looking at could have been that as well as a vacuum leak.
@@ScannerDanner I want to ask a question because I'm trying to make a strategy with the f trims in a road test, I know that pcv egr purge valve leaking injector or leaking valves gives negative f trims ritch condition at idle but at high revs won't the f trims become normal?
@@dimisrambodimisrambo7285 not necessarily, lots of variables with rich conditions
Valve seat loose in the cylinder head.
is that common on the Suzuki engines?
I don't know Dan. I just fought a similar problem same symptoms. As the cylinder temp warms up the seat expands and it kind of reseats itself. That kind of explains the obvious intermittent compression loss you proved out. Then seemed like nothing wrong. Love your channel. I learn something new all the time. Irregardless the head is likely coming off for this problem. Could also be head gasket between #2 and #3. and sealing itself up when it warms up a bit.
Oh also, that was back in 97 on a quad 4 in a 90 Olds calais 442. LOL
Also saw it on a couple SB Chevy engines. Finally figured it out with a cylinder leak down test on all of them.
A guy could be rich if he came to Alaska, nothing but parts changers up here
Brother to be honest and from my perspective what I see in this video is what can happen to technician in real life, looking to fix one thing find another issue
Could be a mechanical failure on an injector no circuit code because electrically fine. My bet is an injector mechanically done. Now not did you not find the evap leak but now you’re thirsty haha
ejector? You mean injector? And no an injector does not cause low compression unless is was spraying fuel all the time causing cylinder wash, which I proved was not the case when I looked at fuel trim
@@ScannerDanner Thank you, another thing I don’t need in my life auto correct. That was merely a guess prior to your testing………
What's the point of this starter test when you can pull the plugs and do a compression test in 10 minutes. You're pulling the plugs anyway to check the plugs for oil, coolant or fuel wetness and to do a leakdown test.
On this engine sure. What about a V type engine where the intake covers half the cylinders? So many examples I can give you where this is THE test to start with. Just crank it over and listen first. 🤔
Well sure, on an engine where you might have to remove the intake for a compression test, it would be quicker, but I'm talking about THIS car where the plugs are right in front of you.
@@atikovi1this is a silly argument. So it's not worth learning then?
I didn't say that. If this was meant to be a learning demonstration, great. Just that in real life situations, the quicker more direct method is usually more productive.
@@atikovi1 maybe you're new here, so that makes sense. My entire channel and every single case study I show is aimed at my students. I'm a technical trainer and have been for over 20 years.
Thanks!
I have a dead Toyota I could use your help with let me know if you are interested
Ask away, ill try to help
6:20
Actually I thought the diagnostic process was clear. You did start with what appeared to be a low compression cylinder that went away.. Hooking up the scanner demonstrated that you had the opposite problem with Positive fuel trim numbers as opposed to negative fuel trim which should have been the case with a leaking injector which may have have caused low compression.
In my mind you made it clear that you were shifting from looking for the cause of the low compression which had cured itself for the moment to looking for the cause of the positive fuel trim. Totally unrelated.
You were verbalizing what you were doing very well and I followed the process without getting the two issues confused.
Just sayin'.
The low compression cause has got to be tough to diagnose when it disappears. Seems like it would require a tear down and careful inspection of all the parts involved. Perhaps not worth it to the customer.
Thank you! This means a lot that you followed this process without the explanation at the end
Next time buy that garbage by junk money and tear it down
Dear Dan, Why do you seem to show up with videos where you're severely lacking essentials tools? It's not an "every time!" thing, but definitely an "often" kinda thing. Maybe it's my perception...maybe it's Russia. Probably Russia. I dunno. Appreciate ya nonetheless - Cheers!
Watch the end of the video. I explain why I wasn't prepared. Thanks!