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Test Your Lean Condition P0171 / P0174 Diagnostic Skills!
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- เผยแพร่เมื่อ 3 ต.ค. 2014
- For you hardcore subscribers and advanced enthusiasts who are familiar with fuel trims, O2 sensor data, and rich/lean condition diagnosis: Test your skills in this episode!
You will need a solid understanding of fuel trim data to pass the challenge so if you are a novice and need to learn about fuel trims, O2 sensors, and diagnostic procedures- or if you just want to brush up your understanding of this critical skill before taking the challenge, see this video first:
Secret of engine problem diagnosis: Fuel trims • Secret of Engine Probl...
Part 2 for this video (where I test viewer's ideas from the comments) is here: • Test Your Lean P0171 /...
You are a national treasure sir. I have been watching you videos for a couple years now and always learn something new. You present data in such a great manner to teach people.
Wow, thanks!! much appreciated!!
@@SchrodingersBox o jave a 08 Chevy Express 2500 6.0 L vortec i jave p0171 p0174 p0300... Ive just found that my pvc hose to have a big crack im the hose right where it hooks to tje head just wondering if this cpuld be my problem im a beginner diyer
It’s possible but not very likely. pCV usually doesn’t draw enough vacuum to cause that but fix it and see!
@@SchrodingersBox okay thanks for replying
@@SchrodingersBox yeah Im waiting on part too get here but I unplugged the hose where it plugs in at valve cover and hooked scan tool up reading trims...my long terms and short terms with PCV valve hose off were both at 24% plugged it back on and short term dropped back to where it normally is after a minute..
Just a thought
Matt, I want to sincerely thank you for making this video series! I have a 99 Silverado NBS with the 5.3L. I've been trying to troubleshoot the cause of my P0171/P0174 for 2 months (due to lack of time and money). This series really hit every possibility, in the fastest and cost effective way, and you are a true "troubleshooter"... and that comes from a guy who is a troubleshooter on fighter jets. 2 days after watching the entire series and taking lots of notes (like you said, don't just stop when you find 1 possible issue) my truck was fixed! and I don't have any of the cool toys you do.
THANKS BUDDY!!!
My pleasure, glad you "get it". Thinking types will enjoy this series very much.
most common problems with po171 dirty maf, fuel delivey and vacuum leak. freeze data show the problem is only under load that eliminates vacuum leak. the problem only affects 1 bank which eliminates dirty maf and fuel pump. o2 sensor shows rich at wot and switching normal. I would check fuel injectors on bank 1 with a fuel injector pulse tester and check that each injector delivery the same amount. thanks for your videos I learned so much from them.
paul miranda Dead on Paul- your thinking is right on. We will do the balance test for sure. Any other things you can think of that might also explain the results and how we would test them?
I just had had a toyota with both banks STFT at 8 and LTFT at 52 and P0171 & P0174. Turned out to be a piece of fuzz wrapped around the MAF wire. Removed the fuzz and a shot of cleaner and instant fix confirmed on scanner graph. I used all of Schrodingers thought processes to get to the MAF. Thanks Mr Schrodinger.
Might I add that AZ free scan wanted the guy to buy a $110 O2 sensor before he brought the car to me.
If I suspect a part is the problem I usually check it with a multimeter where applicable and I clean sensors, check vacuum lines etc. Need to watch this one a few times Matt and I am going back over the fuel trim videos too. Great channel.
This is a good example of why not never just go off a trouble code and always look at relative live data for other clues.
Exactly!!!! I would say about 85% of the time the issue is not the actual part mentioned in the code. 85% of the time. On any codes mentioning O2 sensors- probably it's up to 95% of the time. Of all the check engine lights I've ever fixed, only 2 proved to be bad O2 sensors yet it's the first thing people change.... after plugs and wires of course.
Love them parts changers!!!!
I was a GM mechanic for 20 years and had a wonderful time, all i did was short blocks and engine rebuilds, I was the only guy on the line who like doing them and i got extremely good at one point, I was young enough to install manual transmissions without the need for a transjack, just pick it up and slip it in.
BUT But but....When i had to learn an all cars later, I was spoiled and had no experience, I got over it, but was never as good with any other cars, Nice video.
i just found your channel while trying to fix a 5.7 that hesitates. i like your format (instructor giving quizzes) and you are quite entertaining. keep it up! ever spend some time with performance Audi products? be careful, I used to think American muscle knew no equal. rs7 Performance Premier made me reconsider. being a physician you are able to test drive one without being an imposter/ tire kicker. do so. Those Germans are pretty sneaky a 4 door super car, its almost criminal.
That scotty kilmer choice though....... 😂😅😂😅😂
Hi Matt, a fantastic video, I have liked a lot of the questions during the diagnosis, this time you will overcome. Please, I would like to do more videos like this. Thanks Master, thanks for your time and for sharing your knowledge with us. Thanks Matt.
Matt. Your a great tech. I enjoy watching you troubleshooting. All your videos are awesome. Don't be a parts changer.
I appreciate that! Hahaha don’t be a parts changer is a great code to live by.
Thank you so much for all of this. I am getting a lean condition bank 2 CEL after decelerating or coasting. I am getting misfires also mostly on cylinder 8. Its not the maf, map, or 02 sensors. coils wires and sparkplugs are also new.
Now you can easily diagnose it!
You're a great instructor. I got the right answer right off the bat! But, I didn't watch your fuel trim videos multiple times. Repetition is good for old dogs.
Trust me. This is not wasting my time. Your videos are golden.
I love all of your videos that I've seen, but the graphical representation of the "ricer flyby" made me laugh out loud. Just one more reason I love watching these.
I watched parts of this video an all of part 5. I know exactly what your problem is! There is a lose nut behind the wheel :)
Man, you had me for a second there! How about I fly you down here and you can do a case study on this one. It has me beat. I just spent 2 hours confirming O2 signal on both banks is getting to the computer- it is, and O2's switch and react correctly with vacuum leak and propane. No vacuum leaks at all- verified with a smoke pro (smoooke Prooo as you'd say lol). Cleaned MAF. Why is this stupid thing showing lean under throttle? Got more videos coming up this weekend if you or your students want to take a stab it.
Schrodingers Box Hi Matt did you consider my thoughts on the air injection pump as a vacuum leak . The smoke test would not have shown a leak there. Although the pump was not active during your testing, would it not be possible for the valve on bank one to leak O2 into the exhaust manifold and cause a false lean condition. Danner would be the guy to know how to verify a bad check valve on bank one or is it even plausible . Is there a spot to smoke the AIP lines and see if it holds pressure ?
Matt, have you checked exhaust back pressure? If you have a dual cat system maybe the one bank that isn't plugged is getting all the fuel and the bank that is plugged is therefore having lower trims. Worth a shot, you've tried everything else that is logical. Keep on doing these videos, their fun.
Did AIR test- negative. will be editing new video wth a lot more diagnostics, AIR is incouded in this
Rear O2s react identically to environmental variables and aboslutely no drivability problems = no clogged exhaust but good idea for a bank specific idea. This problem is not bank specific I believe, at least as far as a mechanical issue.
Matt. I just wanted to let you know that during the valve adjustment I performed myself on my 2006 Acura TL, I used your method of turning the crankshaft with an over-set torque wrench as a massive ratcheting breaker bar from the land of intelligence. I have multiple misfire codes during WOT. (P0300, P0301, P0302, P0304, recently P0306, all usually pending unless I keep the WOT going despite the flashing CEL.) it appears the misfires begin at 3,000rpm, but below that, there is no misfire count. I recently installed an OE fuel pump module, as while chasing this misfire condition for over a year prior to finding your channel, I had installed a Delphi fuel pump module in February as part of a near weekly parts cannon entry because I found it for cheap and figured the in tank fuel filter neede-… you know already. It turned out to cause a starting condition, P0171, 01714, and driveability issues that were rectified by the genuine fuel pump module, whereas the Delphi pump did not originally fix my misfires. I am now suspicious of my injectors, but this unforgiving, returnless system with integrated pump, filter, and pressure regulator, and no way to test fuel pressure under load to my knowledge due to needing to remove the intake manifold to test fuel pressure at the rail, I’m feeling stumped. I lack scopes.
Ok so what data do you have? If you don’t have fuel trim data, fuel pressure data, timing data, compression data, or spark output data I’m not sure what you are going on that indicates a fuel pump was bad?
@@SchrodingersBox looking at STFTs and LTFTs and their reaction to throttle led me to replace the pump which did resolve the P0171/P0174. the multiple cylinder misfire under load issue had been happening prior and continued after replacing the pump
what was the LTFt and STFT reaction to throttle?
@@SchrodingersBox LTs were maxed out at 18.8 and short terms varied but always increased and then leveled out when I raised the RPM. car is MAP only. I should have mentioned in my ramblings earlier that I recently did a timing belt kit. car has always sounded like compression is good in “clear flood” scenario (with fuel pump relay removed or Delphi fuel pump after 8 months) as well as numbers have tested in the high 180 range
I don’t see how you conclude a fuel pump from that but whatever the case there unfortunately isn’t any data here to be able to even get a direction. Wish I could help but there’s nothing to be able to even determine a direction with.
Regarding further testing to diagnose your P0171 issue, First, I would go to Mode $6 data, in Global OBD II, to see if there are any active misfires to identify the offending cylinder(s). If yes, then I would consider an injector balance test (assuming I had access to an fuel pressure gauge and I could activate individual injectors with a bidirectional scan tool (If no bidirectional capability or support, then use a Fuel Injection Pulse Tester (e.g. OTC 3398)). If no misfires, then I would pursue an exhaust leak. To test for exhaust leaks, obviously one would need to smoke test the exhaust with a smoke machine (e.g. Smoke Pro).
johnwrench4speed Dead on as always John. I will actually be doing the balance test using my AUto Enginuity.
A long, long time ago...you were my most watched channel and probably one of the first I subscribed to. Then for some reason that only TH-cam can explain, you disappeared from sight...and short term memory. Fast forward to current time...VR6 fuel trim issues. Upon doing some research, came across these amazing videos from years back. Still some of the best out there. Just wanted to convey my appreciation for the help. Hope all is well.
Wellcome back... Wondering if you happen to be "BchrisL" by chance? You sound like him.
Schrodingers Box
No, have never used that handle / alias.
What i'd do is, disconnect all four of the fuel injectors electric connectors. (He's furious already) use a paper clip to jumper those connectors to send directly through the pcm with no load, find a soft part of that trans am and set it on fire, then buy you something made in Japan, this concludes my diagnostic suggestions. Lol btw thank you Matthew, for a highly entertaining and super informative channel.
Had me worried for a second there!!!!
Haha my personal car is a mustang with a big ol v8. Actually if you watch a ton of this channel, the above paragraph is like a distillation of his pet peeves, be it a 1.2L racecar running 50lbs of boost, or shorting directly to the ECM.
Using the scan tool I would test the fuel trims and O2 sensors at idle by producing a small vacuum leak in say the brake booster line. Determine if everything (Bank1 and Bank2) responds as expected to a small lean condition. Spray some propane into the small leak and see if everything responds as expected. Basically, go to a known "good" condition and perturb it and see if you get the expected result.
Agreed- validation the O2 is reporting accurately is a valid step. I had a different idea on how to do that but will integrate yours as well.
So i answered all your questions correctly. Haynes Manual jockeys...?
Back in my younger days a friend of mine put petrol in their new diesel car, easy done when you convert to a diesel after many years driving petrol cars. New cars have an Anti-Syphon mechanism down the filler spout so getting out the fuel without taking off the tank was not easy.
He paid a garage to have the fuel taken out and a new fuel filter fitted for a rather large cost. A Haynes manual indicated where the fuel tank could be accessed from without removal, this was under the rear seat and could be done without taking out the fuel tank.
The large charge from the garage could have been avoided by reading a Haynes manual to locate such a easy simple port hole to remove the tank cap an fuel lines to syphon, clean and do the work yourself.
Since this i consider information provided by the Haynes manual very valuable, as for Scotty Kilmer, Y U hating on him?
Fuel injection is a wild fairground ride of fuel economy and performance but Carburettors sound and make you feel good. Can you tell, I have a passion for naturally aspirated engines with float bowls...?
Nothing beats the sound of a wide open Dellorto/Webber butterfly with trumpets.
Wow great videos!! Im learning soo much, plus learning how to properly read my code reader... still don't know why all of my banks show a 24- 35% positive lean on all my STFT and LTFT.. but ill keep watching to hopefully find out. Lol
To find out I suggest watching my video “secret of engine problem diagnose - fuel trims”. it explains everything.
Great
job explaining fuel trim and problems. Thanks!
My best guess is that you may have a loose or leaking exhaust manifold in bank 1. I would take a bottle of propane and introduce propane along the manifold seal while watching the fuel trim for bank 1. Dropping the hammer on rice burners will create a lot of exhaust back pressure.
Separately, I enjoyed the quiz format. I had several DTCs Friday including P0153, P0137, P2098, AND P2096. Afterwards I recorded O2 volts, fuel trims, and rpms on Autoenginuity and I have that file. I diagnosed the problem this morning using the recording. It is a parts changer special right up your alley. LOL. Would you like the file for a future video?
Sandbag1300 Sure I'll take the file! private message me and I'll give you an email addy to attach it.
Also good point on the exhaust leak- totally valid and I will test accordingly.
your awesome dude. been a mechanic most of my life, you make it fun again. And leave old scotty alone, hes a good informative guy as well.
Gene
ps
my 2001 4.3 jimmys 171 and 174 codes have been driving me nuts. im not a parts changer but i'll figure it out.
Thanks. If you have both the 1 and 4 you want to think of what would affect the air metering for the whole engine. Induction sensors, fuel pressure and leaks between the TB and MAF are all usual suspects
Good refresher, thanks Bernie. 🙂
it's 2 am and i can't stop watching this channel, damn you mat, greetings from argentina
I'm Hooked! 20 year mechanic here and your great!
Great videos. I'm here a little late for the quiz. First time learning how to troubleshoot with a scanner and came across these vids. Anyways, greetings from Grand Junction CO.
Oh wow man I love grand junction!!! I’m there for work a lot. Thanks for watching!!
@@SchrodingersBox Wow! Crazy news on TV tonight... Anyways, man I Love the Trans Am. My dream car. I'm facing the fun P0171/P0174. Unfortunately my scanner doesn't have a long enough cable to watch STFT as I spray carb cleaner searching the vacuum leak. Truck is 2003 F150 5.4 2v. I have 28% LTFT on both banks. A smoke test is definitely what needs done at some point. I don't have a smoke machine but plan to try and make a simple one. My guess with my beginners knowledge is that I have a intake manifold leak on both sides. Hoping I'm wrong, because that's a big job for me working under a shade tree lol.
I had an issue recently with my 2002 Holden Commodore which runs the 5.7 litre Chevy LS1 engine where I drove it after that it sat outside for a few days & had a hesitation when cold.
After I filled it up with fuel the next day the CEL display came on & the fuel trims Maxxed out at 25% on both banks,for whatever reason,my scan tool didn't read a lean fault code.
I tested the fuel pressure which was at 47 psi (it should be at about 60 psi) & the fuel pump was noisy.
I decided to replace both the fuel pump & regulator for just under $50 AUD (the whole fuel sender costs about $100 AUD on EBay),the regulator is a Buick park avenue one which I bought for $9.99 AUD,the pressure had to be adjusted in a bucket of fuel whilst running the engine,it was set at 61 psi which is the best I could do.
The fuel trims today were at 10.94% on both banks @ 100 km/h (60 mph) at cruise speed with an ambient temperature of 23 degrees Celsius & a coolant temperature of 100 degrees Celsius.
Fuel trim under load was at about 7 - 8 %.
So I'm glad that problem is all sorted out now.
..
Fantastic Matt you make a difficult subject fun. Ok I'm going out on a limb here taking a chance on getting a punch in the throat , but here it goes. Both O2 went rich on a WOT, so fuel delivery is capable of adding fuel. Live scan data showed adding fuel bank one but you say no drivability noticed. I am leaning towards a fuel delivery problem from injectors on bank one. I would do an injector balance test to see if you have an injector not spraying equally.
Steve Rob Thats about 7 votes for balance test (mine included) and indeed it will be done on the follow up video. Your rationale is dead on. No throat punch, but a ticket to the 2% community lol
At his point I would rule out a vacuum leak because during a load the largest amount of air is metered air and a vacuum leak would be a minor contributor to the problem.
I would listen to the injectors for inconsistent sounds comming from one, perhaps with a screw driver used to convey the sound. I would check the voltage on each pin of the injectors relative to computer ground for consistent voltage difference between pins of each injector by back probing the electrical connector. checking for less current draw inside the injector due to high resistance electrical connections or internal failure.
These I would test in an effort to discover which injector might be delivering deficient fuel quantity.
First person to explain it where i actually understood. Thanks
Another good video you're kind of right about Scotty he's just trying to make a living too and keep the local auto parts stores in business thanks for the education
I'm looking at the graph. I truly believe it's the O2 sensor. I clean mine up just a little bit not too long ago. And then on day two it came back up only because I cleaned it, but I didn't use. Gasoline like they say you should use. I use brake cleaner to clean it off. But I will be doing a smoke test real quick. Just curiosity.
Geeat videos just swapped a ls2. Into my Jeep and chasing this exact issue
This was an AWESOME video, 🙂, i bet 'Scotty' really watches this channel too 🤥!! i always crank up your video's to 1.7 X above the 'normal' speed, as then it sounds like you're kicking ASS !! Thanks for all that you do, and please keep up the great work , Bless 😇
thanks and good tip on the speed but I hope I don’t sound like a chipmunk at 1.7X lol. well then again- maybe that would be even better.
@@SchrodingersBox nah, nothing resembling a 'chipmunk' 🙂, just simply AWESOME, and not for faint hearts, for individuals who aspire to be 'PIONEERS',,,but you lead the pack,,by a mile,, 😎👍,,keep up this top shelf, high octane,turbo charged, multi faceted education 🙂
Roger that!!!
@@SchrodingersBox Be blessed, 😇
Hi Matt, Great Stuff! Got to keep doing them like this. The Injector Balance sounds logical for Direction to me because I believe you said you have a Schrader Valve handy on the Fuel Rail to hook up a Pressure Gauge. It make for a quick and easy start in your Direction. But it also raises some questions. If one Injector is somewhat restricted and or partially shorted internally, would you not get a hiccup/dry misfire under load? Also if the Injector was restricted, at WOT why is the Bank 1 O2 going fully rich? If you are saying that the Computer is calling for more and more fuel because it is detecting a lean condition under load and that is why the O2 is going rich. At WOT and the engine is inhaling tons and tons of air, would the Computer/Fuel Trims be able to compensate for a partially dry cylinder, enough to send your Bank 1 O2 fully rich?
Just a hunch, could there be a small exhaust leak upstream of your Bank 1 O2, or could the bank 1 O2 be a little lazy? Just a hunch, not a guess, so I dodge the punch in the throat.
Billy R Ha no throat punches when your arguments are valid- and they are not only valid but sound. I did not show it but there are no misfires at all even under load (which is when you would expect them and actually surprises me). But regardless you are dead on and the suggestions will be executed in next video.
Injector balAnce test on bank 1..Matt you are natural, great showmanship you should submit some your vids to one of automotive channels get a 30 min segment for engine performance diagnostics..
fivefortyeye540i Thanks 540, and agreed- injector balance test would be the easiest to do given that I have AutoEnginuity and a schrader valve on the rail.
We'll see what happens as the channel grows lol but yeah I started to get like that crazy guy on Fast n Loud for a minute there lol
I enjoy the amount of knowledge I obtain from your videos, they've actually helped greatly getting my grandpa's truck running again. Favorite parts thought are you jokes about that Terd with lips scotty kilmore
Thank you for your very informative video bro👍👏
I have an Audi A6 2008.
Vehicle: Audi A6 C6 4F 2.0L TFSI 2008
(4 cylinders) only one bank.
Only P0171 no other codes.
System too lean at idle bank1
Freez frame DTC : P0171
Engine load : 20.8 %
MAF : Air flow rate. 3 g/s
RPM: 742
Fuel rai pressure: 688.92 psi
Short term fuel % trim : 3.125 %
Long term fuel % trim : 0. %
Fuel / Air ratio : 14.63 %
No apparent vacuum leaks.
Any idea, appreciated.
Cheers.
Nothing can be said about this data- there is no curve against load. You can neither suspect nor rule out anything from a freeze frame. All we can tell from this is it can't possibly be a vacuum leak and nothing more.
@@SchrodingersBox Thank you for the reply 🎉
Cheers.
What would be interesting is a person with a common problem and the ability to provide graphs as needed to provide you with ongoing requirements as required by yourself and then attempt to diagnose the problem.
The best educational youtube channel I have found on diagnosis cars! Great channel wowwowowow thankss
If you’d lived close to me I’d give u two of my checks to diagnose my cars lolllll
Your a Diamond mechanic
thanks my friend but I would diagnose them for free!!
I would say to check for a vacuum leak on bank one by spraying down the vacuum lines with brake clean
Check the vacuum lines to the brake booster and PCV. ScannerDanner made a video on a Pontiac that had a brake booster issue causing a vacuum leak which then dumped fuel during load. What are the chances you've crisscrossed vacuum lines during a previous project? It's not a bad fuel pump because the car would be misfiring during heavy acceleration as the injectors dry fire. You would definitely see P030x codes for that one. On my car the PCV is between the MAF and TB so a leak there would cause an issue on both banks (not your issue) however also on my car is an EGR that only receives part of the EGR gas from 1 bank not both. Depends on your car configuration and really helps to know the Trans Am in this case (which I do not). Worth mentioning to your viewers that this kind of thing can be caused by a vacuum leak in the EGR system if that system is only on 1 bank. Since EGR only operates during specific times programmed in the ECU you might see different circumstances where A/F is affected. 18% TPS @ 30 mph (light throttle and cruising speed) seems bang on for an EGR leak if your EGR is only pulling from 1 bank like mine. Since you have one of those snazzy OBD-II thingies you can pull up and compare EGR data against fuel trim. Again depends on the specific vehicle but an answer on par and worthy of the intellect you expect from your subscribers.
EGR has no effect on A/F ratio on a MAF system, and hence would not have any effect on fuel trims. Your vehicle may only get EGR supply from one back, but it distributes it to both banks once the valve opens. I'm not aware of any vehicles the get EGR supply gas from both banks.
gojudude My point was to check for an air leak in the EGR system. I had an EGR pipe rust through that gave me an endless amount of issues and took me years to find because it was a small pin sized rust spot. That would still show up on the MAP in this system. I don't have a MAP only MAF and it will definitely screw with A/F just like any air leak. I didn't quite think that one all the way through for this case. The MAP acting as a backup was a great design decision. Makes me wish my car had that setup.
*****
Checking for an air leak on the EGR system is a valid point. However, The MAP in this system (the Trans Am) has no input whatsoever on fuel distribution, it is there only for EGR monitoring. Nothing more, nothing less. As far as your vehicle not having a MAP, then it has an EGR sensor or some sort, like Fords do with their PFE and DPFE. As for your leak on that pinhole, if it was letting outside air enter through the pipe and go into the intake with the EGR gas, it would have to be an exceptionally large leak to effect trims as EGR doesn't work at idle unless it's a throttle by wire vehicle. Other than that, EGR is inert, and doesn't effect trims on a MAF vehicle because the MAF is not, and I repeat, it is not measuring the volume of air, its measuring the mass, or density of the air, and doesn't need correction by the IAT or BARO like a speed density system does.
Well I failed that test miserably. In my own defense I'm an OBD-I owner and fuel trims are a foreign concept. I laughed my ass off because you did indeed get me and absolutely loved the answers. Brilliant.
OBD1 had fuel trims also, they were called integrator and block learn.
Yes obd1 G M has fuel trims. Stft are intergator and ltft are block learn with a scale of 255 being lean 128 being 14.7 to 1 anything under 128 going rich.
I have a special version of Ford EEC-IV installed in a Mazda where Ford unkindly removed the live data port capability. Otherwise I would have the same ECU setup as a Mustang. :(
I think EEC-V is when ford went to a 16 pin ALDL. Mode 6 will have valuable information for you.
*****
Yes, for the most part, eec V is when they went to 16 pin dlc's. Some earlier t-birds (94-95) and lincolns had 16 pin dlc's, but they were only for ABS and SIR diagnosis. Even though there was a 16 pin dlc, one still had to retrieve info from the eec iv connector under the hood. I rarely use mode 6 except to view evap data. There's good info in mode 6, I just have other ways of seeing what I need to see. Remember, mode 6 is one the federal side of the PCM, not the manufactures side, and theres more data on the manufactures side of the PCM.
I like your videos a lot, I learned a lot from you, I feel sorry for those stupid comments from ignorant people, what they don't know is that they waste there own time, thanks Matt.
Thanks man!!
thanks for all the great videos and all the different ways to look at them keep up the good work.
OK, a car running lean on one bank. We can eliminate MAF, MAP, O2B1 because of .1 -- .9 swing, I think that leaves us with bad fuel injector. A power balance test is in order?
Indeed!
I have never heard of an injector power balance test. Interesting. So, maybe a clogged or malfunctioning fuel injector in bank one? I would like to learn more about this possibility.
But, let's say that one out of four injectors is malfunctioning. When the injector fuel delivery pulses are increased in all four injectors to compensate I would imagine that would cause a mis-fire in at least one cylinder. Plus, the fuel trim seems to increase more when driving the car at rpms versus revving the car while in neutral. That to me says exhaust manifold leak because of the torque on the outer engine caused by the drive shaft.
Hi Matt, I like the game that you proposed, I would review the injectors bank 1, A shorted injector would do the O2 sensor will report lean.When we accelerate the amount of fuel is not sufficient and PCM open more time the injectors, because of this we see increases LTFT at banc 1. I think the problem with this car is a short injector, wiring fault or fault pcm signal to open a injector. Thanks for your class Matt,
What you describe is an open injector. A shorted injector will constantly dump fuel causing an extremely, extremely rich condition. But even so- if there was an open injector- you are right, there would be a lean condition on the bank due to the unburned oxygen HOWEVER the lean condition would be present even at idle AND there would be misfires every cycle and driveability problems. It is definitely not a shorted or open injector (which will be shown on the balance test) but it could definitely be unequal fuel delivery from an injector- i.e. partially clogged. However the fuel trims at WOT argue against that too. But your thinking is very accurate.
thanks for your reply, I'll watch the video again to try to detect the problem, thanks Master
Swap o2 sensors around see if it switches banks
Doing a injector balance test is defiantly the next test you should do. But I am going to go out on a limb and say that will not be your problem ! I think you are going to find a air leak in exhaust in bank one. And the o2 is working the way it should.
Holy crap this is precisely what I think. Verbatim.
I second this motion. Check the fuel injection system first. However I would take the exhaust leak test further. The car has an AIR system on it. I would check for leaks and check the components of the Air Injection Reaction System around bank one. I am not completely familiar with this system, but after looking at the AC Delco site. I think I see what could go wrong with the system.
Defiantly
Awesome video, always learning something new from you. 👍🏼
Glad to help!
One more thing sir, if we press gas pedal down a very little, in idle, the system will shift from Closed Loop to Open Loop.
yes that’s because the system is going into open loop since it cannot control the closed loop variables. it’s called “open loop 3 mode”.
I would do a bank 1 sensor 1 response to a man made lean condition (vacuum leak) and see if there is a lazy O2.Then a injector balance test with fuel pressure gauge connected to the fuel rail. Record rest pressure then energize each injector with a timer and compare the fuel psi drops.
My thoughts exactly! Though i will test for lazy sensor a different way.
Just a thought. How are you going to Test the the O2 response?
Switch the O2 sensors on each bank. If the problem moves to the other bank then mystery solved, it was a bod O2 sensor 100%
Schrodingers Box so your just a parts changer lucky you don't fix cars for a job this is not how to fix cars by just switching parts and seeing if its fixed I know its the easy way and this is how most people fix cars .but your TH-cam channel was all about the science of how to test and be 100% it was the part before we fit new parts not just switching parts from one side to the next or from one car to the next please lets us all know that I am wrong about this thanks
Schrodingers Box your being a parts changer.
Excellent diagnostic information.glad i found your channel.
Welcome aboard!
Hi Bro, could you do examples of testing procedures on ASE A1? I subscribe and I always dig all of your content. If you read this question, please let me know! Thanks again for delivering outstanding content!!!
Hahaha.. this my 1st PID to look at.. thanks sir..I have learned a lot from you and all of this make sense now... thanks again
Great to hear from you again!!
Man don't change a thing. Enjoying the channel! I like the to the point teachings and do crack-up often on your sarcasm. (side jokes)
Matt Veillon Don't worry- nothing will change. This style has worked for me very well both inside and outside of TH-cam.
i will go after injector balance test and check the o2 sensor not mass air flow sensor or vacuum leak for the reason of this last two will affect both bank at same time with same readings on fuel trims
+Luis Baez If I recall I thought the same and indeed do that later in the series. Good thinking!
My first guess would be an exhaust leak causing the long term fuel trim to go lean overtime. I think this because you're not having any driveability problems. Briefly clog the exhaust while checking for leaks. Is the 02 sensor bias rich a bit on that bank? My second guess would be partially clogged injector causing a lean condition I just think you would notice it somewhat under load. Doing the injector balance test would be good to eliminate this.
We are in total agreement James- thanks for the comment, I believe this is your first on the channel. In dact, I was going to put my money on an exhaust leak until the video i just released today.
I am new to this and learning, I would look at testing fuel pressure and see if the pump is not working correctly. If the pump is weak wouldn't that effect all banks and injectors, unless one injector for bank one is clogged. O2 sensor would be what I think the issue is
correct on the fuel pump- it would affect all injectors. however we know the O2 sensor isn’t the issue because of the fuel trim response. it’s definitely not an O2 sensor issue.
@@SchrodingersBox
Could be a bad or clogged fuel injector causing the issue
No because we see no misfires or injector pulsewidth correction. keep watching to the end of series- it continues on another series. look in description on last video
I'm actually very excited to find out the cause because I have similar problem with my Corolla :D. LTFT goes high under load. I have of course looked for simple and unlikely stuff like spark plugs, vacuum leaks and other leaks and did O2 response tests (was switching fine and did respond to lean and rich condition). Then I had my fuel pressure checked which was perfectly within specs. Then I took my injectors out and cleaned them (not much dirt came out) and spray pattern looked fine to me in all of them, so no much effect. I came to conclusion that my MAF was going bad and replaced it (of course I tried to clean it before). And it had a BIG effect on LTFT, dropped from +10 to 4 at idle and from +20 to 12 under load. But the characteristic is still there, so what the heck could still be the problem? Of course there was no way for me to measure fuel volume of injectors so they could still be potentially the issue. I also don't have any drivability issues, just a little higher fuel consumption.
And as for this Trans am case, I think the problem is with injector(s), maybe clogged/dirty.
Von Brontos We shall see! If your corolla was a 4-banger then all your diagnoses were valid, but if it was a 6-banger, hopefully now you see that much of the tests could have been ruled out.
Cleaning a MAF is a good idea anyway though- I do it every air filter change.
Schrodingers Box Yeah a 4-banger :P
I like the sarcasm
well the next question, why the STFT descends?, the STFT descends because in one cylinder not have blast but the others have more fuel than you need and O2 report rich condition and PCM adjust STFT.
Never mind. You caught it. I bet this would have been fun live!
Vacume 😂. I'll keep it mind!
my 2000 Tahoe takes forever to start in the morning each time I leave the key on enough for the fuel pump to push gas and pressurize after about the third attempt it starts once I do that for the rest of the day the truck runs fine starts right up accelerates well no missing no problems I'm suspecting the fuel filter issue but as for the rest of it I'm at a loss I did have a lean bank one called earlier but it's gone and it has not come back I don't have no codes showing but I do have a truck that starts very hard on first startup in the morning and then runs fine for the rest of the day
what’s the static versus running fuel pressure readings?
This is what I’m looking for to be explained the lean and also diagnosing the system
According to your rules of the game, the answer was c. Chevy don't work the same as the "other car" ;P For the first question.
The Chuck Norris reference. Lol
Thanks dear
My 2001 Explorer Sport P0174-only came after several long cranking times to start.
sounds about right. that would be a major simple clue indeed to the cause.
yeah . i was kidding i find what you offer and how to explain is very useful and is not competitive for you . i have learned so much in this short period . thank you so much for this \ i am not very good in writing English . but i speak well / .
I don't know what to say, you are just a professor!
Matt on yesterday's TPS . I would like to say I don't subscribe to the phrase "the only stupid question is the one you don't ask". Unintended consequences during the test showed me there is no conductivity between a TPS and an IAC. While the TPS was disconnected am I correct to assume if you opened the throttle plate the IAC pintle would have closed and stalled the engine for lack of fuel. Also did the TPS have a ground at the sensor to the ECM provided and why did you need another ground ? I pay close attention to your vids because you do and say things to see if we're paying attention , one "C" in vacuum better not put a "E" LOL , so you have two options - 1 - I'm correct and 2 - I'm Nuts . 😜
Steve Rob Steve, based on other comments as well as yours I do need to revisit the cause of the engine speed increase with TPS and it will involve pulling IAC data. My thinking... which I agree may be wrong... is that the IAC is a non factor since presumably you would expect IAC to close if anything with increase in TPS, so I didn't consider it as reason for idle change. I though idle change was due strictly to fuel addition which of course I did not detect with fuel trims because I wanted to make it so ONLY the MAP and MAF could be used to detect the bad TPS signal.
Another analysis is in order to answer the question for sure and this is exactly the reason for my idea of "Schrodinger's Mailbox" where I can revisit stuff like this!
In part 5 I saw 7-8% LT, that dropped when you raised the RPM. Without watching all the parts, what was trim number at a steady 3000 rpm?
ScannerDanner Yes you are correct Paul, and it held steady BUT later on while driving it reverses and the LTFT's will be at zero but when I accelerate the FT's increase easily 10-20 sometimes more. The "vacuum leak" pattern happens only in the first 10 minutes after CL. The "fuel deficit" pattern happens later and stays consistent. But fuel pressure fine, cleaned MAF, no vacuum leaks confirmed by smoke test (which also confirmed no vacuum leaks). Both LTFT's adapt to variables in generic mode but bank 2 absolutely won't budge in enhanced mode at all- seems to draw a substituted value- but from where?
I got it right! So in tradition on this channel I will gloat and be full of myself!
No- you GUESSED it right. When you actually understand what I am doing then we will talk about your acceptable behavior. But not a minute before then.
Thank you
Short and Long Term Fuels 1 should be below 10% combined ideally. Those % in the graphic are way to high. So a vaccum leak still a possibility.
your channel is great.. but i learned alot with Scottys channel as well... dont hate, plenty of room on the internet for multiple car fix channels
Just curious what you learned on scotty’s channel? I have yet to see one single useful EVIDENCE DRIVEN diagnostic information whatsoever. all I ever seen is parts cannon ridiculousness and “these computer controlled cars are crap- don’t bother with them” kind of stuff like you see in the automotive chat room forums from people clueless on technology and diagnostics.
The day I see him do a cam sensor bypass instead of throwing a cam sensor AND a crank sensor at a cam sensor code I think I’ll fall out of my chair.
Best way to make a trans am run better is grow a longer mullet and turn up the motley crue cassette tape! Alot of guys try zombie green RIMS.
Hi Matt, sorry for my English, I meant "I would like see more videos like this".
I’ve been dealing with a lean condition b1&2 on a 05 gx470. It’s acts like a vacuum leak as the Ltft’s calm down to below 5 under hard acceleration. Mid 30s cruising 35mph under vacuum. O2’s appear to be reading and reacting correctly.
I’ve gassed around the intake and haven’t had any fuel trim reactions to propane.
I have not got the fittings to do a fuel pressure test yet. It runs good under hard acceleration, but surges above 60 under light acceleration.
Has anyone seen the sais check valves not close fully and allow air into the exhaust without codes?
I was Wright on both questions so it means I was a good student sir
OK, Time for me to make my guess. First off I think it has to be Fuel. As that's the only problem that the single bank situation supports. My Tech 2 does a power balance test electronically which I think would be where I would be going next. That should tell me if you've got a bad cylinder on that side or not. The problem with the power balance however is that it doesn't tell you if it's the injector or the coil over plug which I believe these LS-1's use that's bad. OK, let's whip out the PICO scope and that should get the job done. Stuzman52 are you listening!!!
Agreed except other explanations for a bank1 specific issue exist besides fuel. Exhaust leak and O2 sensor would be two of them. But a balance test is coming, for sure.
I like the scope and scanner videos the best
Hi Matt, I see the video again and I have a new theory, It's possible the car has an injector dirty?, We have a problem with the fuel pressure in bank 1, the fuel pump and regulator fuel are common to both bank, but the injectors are individual for each bank. I think an injector is dirty in bank 1 or the injector has a voltage drop by a bad connection and not open enough. When accelerate there is not enough fuel for a stoichiometric mixture and PCM prolongs the opening of the injector. Thanks for this exercise Master.
Indeed! Manolo! Many people agree with your dirty injector theory for exactly the reasons you stated! We will find out in a week or so!
Ok Matt, thanks and congratulations for your channel.
ohm out the maf. unplug the o2 sensors and check for quick voltage change
Wait- how would unplugging the O2s have any affect on induction metrics? Not following that strategy.
Also, when unplugging the O2's are you looking for Bias voltage or what?
Teacher Einstein thanks for not been like chuck norris and not telling us the answer, all ways test probably theories and get true results 👌👌👌
Bank 1 running leaner (LTFT) than bank 2. V6 engine. Numbers decrease (LTFT) as I accelerate, then increases again at idle. Any help is appreciated. 👨🔧 Short term stay close to 0 when idling. Long term bank 1 at 17, bank 2 at 11 at idle.
Not enough data to make a determination but initially looks like a vacuum leak
I guess I passed. I only had 1 incorrect answer, question 3. On to part 2 of the test.
one tech to another, I like your OCD! vacuum! my man.
Video was very well explained.
Great Info Vid 👍🏽Love Going to TH-cam Mechanic School lol U the Man Teach 💯💯💯
Good stuff. Well explained.
Tnx to be honesr u really are a good teacher
Tengo una troca 2007 ford f250 3v ya cambie los sensor de oxigeno y las bobinas bujias y no hay licks los cramsaht t camsacht y inyector y not pass smoke check tks
I have a very odd issue with my 05 Nissan Pathfinder SE off road v6 4L. I had the p0171 code, but for some reason, it only trips at load after warm up. Something seems to click on, and I can watch the live data just start running up to 25% and staying there until it cools down and is restarted hours later, when it goes back to correcting the fuel trims. Also, the bank 2 sensor 1 goes up to .9v and stays there rich on bank two, so I'm not sure why this happens in conjunction with a lean bank one unless there is a manifold leak on the bank 1 side and all that extra fuel is still registered on the bank two (I swapped out this a/f sensor and captured the same exact readings for both sensors, which also means the old factory one I put back in it is probably still good). I've been putting off ripping into the exhaust manifold in fear of stripping something out without having the proper tap and dies to bail me out. I might lube it up and gradually give it a go and at least see if I can find any leaks hooking up my vacume to the tail pipe. Lol jk vacuum. Sorry, I couldn't resist 😹. I just don't understand why it only occurs under load. Could I collapse a hose or something, or when the fan kicks on or some switch activates it disrupts the O2 sensor signal somehow tricking the computer. Idk. Is there a load switch or something that would just all of a sudden cause the one side of the engine to go lean and the other side to be normal.