Secret of Engine Problem Diagnosis- Fuel Trims Pt.2
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- เผยแพร่เมื่อ 1 ต.ค. 2024
- Part 2 of 2. Actual examples of scan tool data are shown so you can test your comprehension of fuel trim data interpretation from Part 1 and make diagnoses or determine reasonable direction towards a repair without even popping the hood!
Part 1 is Here: • Secret of Engine Probl...
For more advanced Fuel Trim info- see my video on adaptive fuel learn here: • Understanding+Diagnosi...
This video is amazing. I have learned more in and hour than I ever would have known otherwise. Thanks for making it.
Very informative videos . Made me use my brain. I learned a new term too. Stoiciometry. Thanks. You are a great instructor. You really got my attention when you said” If you replace the O2 sensor at this point, your an idiot!”. Made me pay even closer attention because I don’t want to be an idiot. Thanks again.
@@MarioGonzalez-gh5mm Please note that your use of "your" should be "you're" as in "you are". Thanks.
Six years old and still a fantastic discussion of fuel trims and associated issues. I really appreciate you taking the time to make these videos.
I hope you keep making them.
Glad you enjoyed it!
Excellent!!!
Fantastic videos you are a first class teacher ...thank you
you have a good way to explain
Thankyou a ton!!! I wish that I worked with you daily. TO THE 2%ERS MAY WE BE METHODICAL IN OUR DIAGNOSES, SAFE DURING REPAIRS, GENEROUS WITH OUR KNOWLEDGE, AND THANKFUL TO OUR MENTORS!!!!!!!
True!
You have absolutely helped more people than you could ever know!
You just expanded my Short Term Brain Capacity by several billion cells. Now I need a few beers to kill some so my head doesn’t explode. Great job!
There's no way I can thank you enough for such teaching I did my first diagnosis last week without popping the hood using fuel trim data I was a little hasty at first but you put in this video so many great details that I was able to save stress time and money may the lord grant you more health time and wisdom thanks for your time and shearing
congratulations!!!
What an absolutely beautiful and understandable description of fuel trims and how to diagnose where the problem “most likely” is based on the behavior of both the STFTs and the LTFTs. And the importance of validating to response after the repair has been made. Thank you ever so much!
You've done an amazing job simplifying and explaining this complex subject. You are truly a gifted and rare teacher. Be proud of yourself. By the way, I'm 78 years old and don't need to know any of this stuff anymore, but I find it fascinating. Thank you.
jerry im like you im in the inquiring minds need to know croud . if you understand the basic operating principals it makes diagnosing problems easier
Awesome explanations of ST and LT fuel trims. VERY informative and helpful......you really do have a gift for breaking down and presenting automotive diagnosis and troubleshooting methods. Thanks for taking the time and putting your videos out there for us do-it-yourself folks. Much appreciated.
Remember to deal with any physical issues with the exhaust before trying to diag excess fuel trim. Currently I'm dealing with high fuel trim on a 8.1 GM in bank 2. I found a leaking manifold to exhaust pipe gasket 6 inches from the bank 2 O2 sensor. Replacing the studs and gasket this afternoon. Even though it set no codes this leak would draw oxygen into the exhaust ahead of the sensor. Not enough to set an O2 sensor code but enough to skew the fuel trims trying to cover the extra oxygen in the exhaust.
A crack in the manifold in front of the 02 will do that also and can throw rich and lean codes both at the same time which can be confusing
I got a p0171 on a v8 mustang. Under idle both banks look good. Under load the bank 1 trim is high, but it's not quite setting off the engine light again since I reset it. I was thinking maybe something wrong with one of the injectors, but the injectors are only a year old, and they're ford performance injectors.. but you got me thinking maybe there's a leak in the exhaust. I haven't heard anything sounding like an exhaust leak though. Maybe it's a very small exhaust leak and that's why it hasn't set off the engine light again.
@@sk8n854 have you cleaned your maf
What data do you have?
I have a lean condition and a pending high pressure fuel code at idle the fuel trim is normal but at load the stft actually goes to -10 and it is throwing me off not sure what to do
Superb sir. What a beautiful and interesting lecture it was. You are genius. I will wish that you were my teacher i would have a learn a lot from you. But still in these 50 mints i have learned which i have not learned in last 3 years.
Thank you soo much for making this video and upload it in TH-cam. I wish to see more video.
+Asif Ali Wow thanks man! made my week!!!
Been in and out of motors all of my adult life, in several shops. Never have I been blessed with instruction, placed at the bottom shelf as much as be able...like this. You lay it down simple and purposeful, and yet straight to the core. THANK YOU TIMES 10!
Not everyone is apt to teach. You Sir, have been given the gift. May you be blessed abundantly for your part helping humanity.
Brilliant... absolutely - brilliant. Now that I fully understand the concept of fuel trims, it really helps me appreciate how good this guy really is. Not just a great mind, but also a great teacher. By a clear country mile, the best explanation on the internet.
If i ever gave TIME to anything that was worth my TIMER this is the first. You're a GIFTED instructor on being a REAL TECH not a SHADE TREE MECHANIC. Chi-Town realist.
Your a great instructor! I’m a 72 yr old A&P Mechanic and have worked on everything all my life ! I almost gave up in this computer age ! But because of you I’m going down to pick up a device to read my cars fuel trims and components! Thanx your a great instructor!
Sincerely Mark H Wirth
Glad to hear it!! Yes it is a challenge keeping up with technology especially for us older folks but if you can do it it’s very rewarding.
I'm a certified mechanic with 20 years experience and I enjoyed watching this video very much detailed and very accurate great job
Just wanted to say that you did a wonderful job explaining all this. I was trying to explain to my girl friend how an O2 senor and fuel injection works on our Scion. I went to college for automotive and have been working on cars most of my teenage and early adult life but a good refresher is always nice. You explained this better then any of the classes that my local auto parts store holds of the local garages. One thing I was hoping to hear was that all this PIDs are not actual numbers. They are what the computer thinks it sees (meaning corrosion or a defective component or Ecu ecm can give false readings) and then back probing, DMM or oscilloscope is needed to confirm if the ecu is telling us accurate info. Thanks again for a great and informative video.
You are amazing. I just got a P0171 on my car with nearly 200K miles. The muffler also sounds a little louder to me. From your video, that is at least suspect. Thanks.
Diagnosing Turbines, its vital one understands fuel trim........
It took 15 yrs for me to get, understand, what you are freely giving to anyone who wants or has the love for Engines!!!
It just blows my mind what was held back from learning, is now FREE!
Again a huge Thanks!!!!!!
totally agree, he gave a free pick my brain course, I to struggled to understand stft and ltft, read and read, totally confused, and in this one video I feel like a pro. good job dude.
I have watched these 2 part videos probably 20 times over the past 2 years and every time i watch it, there is at least 1 light bulb 💡 moment. Nicely done Matt 👍
Yes these videos are old but still totally relevant and it’s a lot to digest! Once you master this concept, it totally makes you far more capable in diagnostics.
Thank you so much for these videos. They have been a wonderful help in my quest to learn more about vehicles. At least now I can have a more intelligent conversation with the mechanics in the family.
You're awesome! Thank you so much for taking the time to do this. Your teaching abilities are master level. Bless You!
I just happened to stumble onto your part 1 video, and watched it entirely. It was so interesting that I just watched the entire part 2 video, which was equally interesting. Then I hit the subscribe button. You did a fantastic job of explaining how the engine computer algorithm interprets and processes the sensor information, especially related to fuel trim. BRAVO!
Thanks brother!
I can never thank you enough. I learn so much from you compared to other videos I watch.
Glad to hear!!
I thought I had a basic understanding of fuel trims...UNTIL I watched your videos. I now have a much broader understanding so thank you! It gives credence to the old saying, "You don't know what you don't know".
just found this video. found it amazing as you are quite thorough and patient in explaining things. and also your videos is clear, precise and easy to understand. Aloha!
thanks for the comment!! glad you found the channel!
The best tutorial on the subject ! Thanks for the dedication to our learning !! The quizzes are a great way to self-check our understanding . You are an awesome coach !
💡🔑🏹🎯🙌🏼
Probably the best lecture I had. This hour is worth my 5 years in engineering school. Very well said. Respect
Hey, guys. I've been dealing with a fuel trim issue that I'm sort of perplexed by. Thanks to Matt's video series on fuel trims (thank you, Matt), I've learned a lot, and they've given me an indispensable framework to better hone in on related issues. But, I'm still learning.
The issue began with 2 fault codes: P0171 and P0174 (i.e., lean conditions on both banks). The vehicle (2007 Mustang v6), would idle at approximately 25% LTFT on both banks. At around 2000 RPM they would shoot up to 35% LTFT on both banks. Seeing as the dealer tested the fuel pump, I went ahead and replaced the MAF sensor and reset the KAM with a test lead, then followed the relearn procedure.
Replacing the MAF sensor solved for the lean condition; however, now the vehicle has been running slightly rich on both banks for the last 3 weeks, not enough to throw a fault code though. On startup, cold or otherwise, it's been idling hunting until it warms up since I replaced the MAF sensor. At idle, LTFT1 is around -2% and LTFT2 is around -4%. At around 2000 RPM LTFT1 goes up to around -11% and LTFT2 -14%. Short terms are almost the exact OPPOSITE of long terms. So, if LTFT2 is -14% at 2000 RPM, STFT2 will be at roughly +14%.
I can get a more extensive data set if anyone is up for helping me tackle this issue. Anyway, thanks guys.
Wow. May have to watch this series again. Just an amateur looking for general guidance and I am enthralled and amazed by your presentation and knowledge. My long term mental trim is rising rapidly to trend upwards towards the short term knowledge overload. Now, if the long learning approaches and stabilizes close to the short term present data then my composite will be close to the actual. Thanks for your professionalism and desire to share.
Michael Murray
you explained it better than anyone else.
I've been looking for that for a long time. THANK YOU
Your teaching is very clear. I have been working on cars for more than 30 years, and I have never been privileged with a more clear understanding of engine management systems. Thank you!
I am an Arabic and my English is simple i know most of the information. But I've benefited a lot from this video and I'll also explain it on my channel . Thanks alot
I learned so much more from this video than going off for a week for training. The only thing that maybe you forgot to mention is that Ltft takes a while to set and respond. Correct me if I’m wrong but I don’t think it responds quick. Over all this video could save a lot of money and time for people that want to learn. And you make it so clear!!! When I went off to class for engine diag and performance we spent 2-3 days on o2 sensors alone!!!!!! To learn what you barely spent time on to explain but made so easy to understand.
This was very generous of you to educate us on fuel trims to help us diagnose our car problems.
Part 1 and part 2 are……GOLD. Thank you for these videos. I will study these in more depth. You explain this material in a very understandable way and provided EXCELLENT examples I appreciate how you broke this into 2 parts and dug into the details!
I'm glad I watched both Pt1 and 2 just brill, although I will be recapping. Thanks Matt just brill.
new subscriber to your channel, and I am so glad I found you. Thank you for taking the time to do these videos for us do it yourselfers, with the information you give us and the "lower shelf" way you explain it, i am sure you have saved thousand, and thousands of dollars in needless repairs. thank you, thank you. Now i have a question that i did not see answered ( or maybe it was but didn't understand). You mentioned briefly about ltft and stft both being high, but i don't believe(outside of exhaust leak) that you sent a cause our way, or possible cause. I could be mistaken. I have a ltft at 18.8 and a stft at 30.5, i don't have O2 info and i only have a MAP not a MAF. only bank 1 so ruling out fuel delivery, but not sure if i should rule out vacuum leak . I will be watching more and more of your videos hoping to find a direction, and again thank you, you are a great instructor and i would like to give you 10 thumbs up.
Thank you Champ.
I am not a mechanic but have been very curious about how modern vehicles with computers and sensor. Your explanation in your P1 and P2 videos brought me up to speed.
You are a Real CHAMPION👍
Many thanks from EGYPT brother , you are really know what you are doing , keep it up .
I CANT HOW MUCH OF A HATER YOU COULD BE TO GIVE THIS GUY AND THIS VIDEO A THUMBS DOWN
Disliking something isn't hate dude. You're watering down the real meaning of the word.
SheepAmongGoats “disliking” something that is pure data and not subjective is highly indicative of lacking objectivity aka “hating”/personal bias etc.
@thekeyboard warrior Wait till nov you moron when your 10th grade emotional level leader trumpff goes down.
Ive been wanting to solidify my knowledge on this subject for some time. This is very informative video. Just wow
These were terrific- thank you! I really appreciate seeing and talking through several sensors and how they would each respond to different circumstances. I'd also like to hear more about down stream O2 sensors. How can they read 3.2v? (I thought they should read less than 1v. (this is in a 2003 RAV4). Thanks again!
Fuel Trim always left me somewhat confused until I watched your Fuel Trim videos Matt, everything is now very clear! No-one before has quite explained fuel trims in a way that the DIY man (or no doubt even some technicians) can fully understand. You said it would be life changing Matt - you were not wrong.
I know full well, there are many people working in service industries that couldn't troubleshoot themselves out of a paper bag. As an engineer with tons of troubleshooting tools in my toolbox, I want and need data. I now know how to get it, thank you!! This makes perfect sense. Thank you for this set of videos.
I appreciate your knowledge and ability to teach.Your videos have helped me advance further than I can explain.I have only been in the trade for 1 year and now have over 60k in tools and now a heavy line B Technition and now learning to use my Apollo d8 and once again your abilities to teach me supersedes anyone else.Thank you.
Thanks for such valuable input and explaining fuel trims. Lot of CNG installers simply ignore the necessity of matching fuel trims on CNG with that of the engine on Petrol while calibrating, it leads to glow of OBD check light due to lean or rich mixture in most cases due to this.
PHENOMENAL pair of videos wow. Round of applause!!! Changes so many things I've learned over the years and bad habits I've picked up. I too have found myself changing parts sometimes looking for answers, which I hate to admit. But I always complain how no one knows how to diagnose and fix problems anymore. We all seem to have fallen into the rut of just replace it! My grandfather who is no longer with us used to take the time to diagnose and repair EVERYTHING and I always admired him for that. Great job. I have alot of things to learn now.
Very good explanation of Fuel trim and how to use it for diagnostics. Thanks for posting this.
There is absolutely no-one else on TH-cam who can explain concepts like this guy. Every single video is a winner. Unparalleled knowledge - unbeatable!
thanks man!!
@@SchrodingersBox You're most welcome. Keep doing what you do.
I like the way you invent a scenario and force us to think! I learned a lot. For me, it would be so beneficial if you could match an engine's actual behavior to the scan data. You may have already done this, you have so many video's. It would be so very real world. Great listening to you
Great videos. I’m not a professional mechanic so I have to watch them again to remember how it all works. There is a lot of info packed into a few part video. You explain it so well , keep up the good work.thank you
Right on!
I had a similar situation like you mention in the final few minutes of your video. But, both of my STFT were maxed out at +25% constantly. The car was only throwing a 171 code though, so it took some troubleshooting. I was told by everyone it was an O2 sensor, bad MAF, or some other expensive electronic. I hooked my vacuum gauge to the manifold and noticed it would hold steady at 22hg, drop to 19hg, and then hold steady at 22hg again. I plugged the manifold inlet and it held steady the whole time, so I narrowed it down to some piece of vacuum line. Used unlit propane, water, brake cleaner, and everything you can think of and could not find the leak. I built a smoke machine with a paint can, nicochrome wire, car battery, and some mineral oil. Saw smoke coming out from behind the booster and it was a 15 dollar o-ring that rotted away, but had to fix it with duct tape until the part arrived. I was always curious why it didn't setup off 171 and 174 though, since it affected both banks. Having half the code made me think it was just one bank at first.
This man has got it together . He is able to demistify One of the best communicators when it comes to modern automotive problem solving . Many thanks regards p j rose .
Thanks for the tutorial I learned a lot. Found the vacuum leak in my system. Car runs perfect now without check engine light. Saved some money with the repair. Thanks.
I’ve been working on cars for 40 years, you explained it like I was 5 years old which is exactly what I needed- thanks
Hahaha I always thought that if you can get a 5yr old to understand it, you are effective at teaching it. I always appreciate being taught like a 5 year old as well!!!! Never to proud to learn in the most effective way possible!!
Have you made a tutorial dvd on all your subjects which I could buy - your tutorials are A1 - the best I've seen and greatly simplified my understanding on the dark secrets of the computer controlled engine.
+wellermans Thanks bro- no I have thought about it but no plans for DVD's in the near future. But it's not totally out of the realm of possibility
9 years later, wow, just what I needed. Getting my scanner tomorrow. My sons car just stalls mid driving, also on inclines. Had so many mechanics with different opinions and prices. I knew carbs back in the day, this just put me on track.
Thank you sir, I have personally struggled with trying to understand fuel trims. After watching your two part series I can honestly say that I have a much better understanding of how they work. Thanks again for sharing.
Good for you. Understanding these concepts is probably the single best diagnostic ability to have for engine performance diagnostics.
very well done and detailed reminded me how grateful I am and will always be of my instructors and their teaching thank you for taking the time to work on this
Excellent presentation! You could teach college classes on this subject! :-) You helped expand my knowledge! Thank you.
This was truly an excellent presentation on this subject. My knowledge base on diagnosing engine issues has just gone through the roof for a DIYer. Thanks for taking what many would consider complicated information and making it simple.
You sir are a saviour to us DIY guys with your thorough explanation of this type of diagnosis. Thank you so much.
I watched 5 other videos on fuel trims and this one definitely was the best and easiest to understand. Great teacher, great pictures and examples. Thank you.
Just bumping into this and found this information very helpful. You teach very well, keep up the good work man. It is nice to see someone share there knowledge. Your videos are straight to the point and can be used as a teaching tool. You should see some of the boring professors out there, then you will know what I mean.
Thanks for the lesson, i'm novice and looking for advice, you are a great mentor i will watch over and over till i can understand it better! Thanks again!
You're a natural at this! Thanks for sharing your knowledge.
Thanks ; you are saving many people much time and much money and much useless repairs by explaining the utility of LTFT as an effective way to diagnose correctly some of the common problems which cars have as they age or are worked on. Your service is much appreciated and that is something that is a good contribution to the wellbeing of society in general when it comes to keeping cars safe, efficient, and drivers conscientious about their vehicles.
THANKS for presenting this otherwise difficult to understand information in such a GREAT easy to understand format. Your expertise is evident, AND your teaching skills are SUPERB. I am a very old school mechanic that cut my teeth WAY before computer controlled and sensor inputs. Good old needle valve controlled carburetors and point based distributors were then the norm. You have FINALLY helped this old geezer (72 years young) to understand the scan tool readings and how to use them to diagnose common problems in TODAYS engines. My Honda Civic (2004) has almost 225,000 miles at present and finally set it's first P1172, P0134, and P2271 codes. I ran right out and bought an O2 sensor.... but problem persisted….Duh! Now I am equipped to properly approach the problem. THANKS ARE NOT ENOUGH but will have to do. Thumbs up my friend.
Team street glow??? LMAO
Hahaha remember that blast from the past?
Schrodingers Box Lol no I'm only 19 in diesel tech class but the automotive kids all have ricers with the fart cans lol
Schrodingers Box this video really helped me understand a lot, keep up the Good work!
Team street flow lol
These were super informative and the orderly scientific approach is great.
Thanks!
Good stuff!
Now I'm going to put it into practice! Looking at this, I have a better understanding of what the data from my new bluebrive is telling me.
I may have a vacuum leak in bank 1. It's saying something like:
Bank 1 catalytic below threshold or low. But the trims are definitely indicating vacuum leak bank one.
Thanks again!
Thank you. This has been the most informative video I'd seen. Quality is amazing. Clear and Eloquent explanation.
Hi, Good video, I have got 2010 mini cooper S R56 start at the first crank and drive nice and smooth but on the morning when the engine is cold it hard to start I have to crank several times to get started on, do you have any idea what is could be the problem?
Thanks
Ray
You should have been a detective with your forensic analysis of car problems, Mr. Holmes. Good job.
Not even my ASE class explained it this way where u can understand it
It seem that, at least in regards to fuel trim, the PCM has a fairly robust ability to mask minor problems, such as in the examples you gave: dirty MAF, marginal fuel pump, and vacuum leak. I mean, if the LTFT has to hit 24% [I think that is the figure you gave], before you get a check engine light, then even though the engine appears to be running fine, there must be some indication that all is not well. Maybe decreased fuel economy or driveability issues? I would appreciate any thoughts you might have.
+Christopher Eaton Exactly- the great things about modern performance controls is you can have relatively serious issues with a car's input metering but it will ultimately be compensated for to preserve performance as much as possible.
But indeed there is still a 'hidden' issue with the vehicle.
@@SchrodingersBox inconceivable
I work on transmission. However, I constantly watch all videos related to the vehicle in case I run into a problem at the shop that is not transmission related. Some engine sensors affect the operation of automatic transmissions these days. I appreciate your time.
Great video series! I'm an old dog but you even succeeded in making me understand the fuel trim concepts. I really enjoy your videos. Thank you,
super super information and u explain very well this fuel trim issue.
+Bob Parrott Thanks man, this is still my favorite of all the videos I've done.
+Schrodingers Box fuel trim gets better at higher rpm with dirty MAF and worse at higher rpm with vac leak. You stated the MAF totally wrong. get it straight if youre going to try to "teach" people
troopbd Well I would agree with you but then we would both be wrong.
Thanks for giving the complete idiots point of view.
There is no debate- a dirty MAF will show a higher fuel trim under load. IT HAS TO. There is no other explanation as I indicated in the video.
Instead of spouting hot air what is the MECHANISM by which you explain the results you claim?
Yeah, exactly.
troopbd I suggest you actually read that stack of books so you don't make yourself look like a fool then.
Dave Carlson ROTF!!.. yeah he's also an idiot. I will never understand why someone would put themselves out in front of hundreds of thousands of views and be dead wrong. But it happens every single day.
Mr. Schrodinger, what you are teaching is impeccable and extremely educational, I am not at your level yet because I need basic principals and terminology along with sequence of input players MAF, MAP, IAT, O2 SENSORS, AND EXHAUST LEAKS. Today after watching your videos 7 times I got a glimpse of what you where teaching about air and fuel trims short and long and I was very happy to see and hear what you enthusiastically explained, with such determination and definition. I had to read more about fuel trim diagnosis to build up to your level because as you spoke about the fuel trims in some instances you forgot to distinguish for me which one either the short or either the long, so I could not grasp the focal points you where attempting to make when events arise such as exhaust, vacuum leaks, or the stoichygoemetry reaching and resetting at a higher positive reading memorizing long term and short term calling for more or less fuel to balance with long-term it took me a longer time to learn it. I have not mastered reading the fuel trim data however I want to deeply thak you for sharing your knowledge and creativity.
What a fantastic comment! Thanks!!
I've devoted 10 years of my life to the automotive industry, maybe a handful on my teachers had passion like you explaining something. So Thank you.
I'm now in a position where I need to be my own teacher, I'm done parts changing. Looking at buying diagnostic equipment so I can truly diagnose my issues.
Thanks for giving free knowledge!! I'm currently in school and we're starting fuel systems this totaly helped.
Excellent Excellent Excellent video. You're a fantastic teacher also. Can't even tell you how much I appreciate this information. I don't want to be throwing parts at my car. That doesn't save money at all by avoiding the commercial shops (which I have had many bad situations with). I'm not a master yet, but believe me you've brought me farther than I ever was just with these last 45 min
This has been one of the best videos I've seen on youtube. It has been very clear in the explanation and easy to understand. Thank you for these videos
Thank you so much for these videos! I have a 2004 Ford Focus SVT that was running lean p0171 and had taken it to Ford and a local shop and both couldn't find the problem. After watching your videos I knew it had to be a leak in the exhaust before the OS. It was a broken bolt where the exhaust manifold attached to the catalytic converter which allowed air in next to the OS.
I'm having the same issue with the 2009 GMC. After tightening those bolts how long does the computer take to drop the LTFT? I'm hoping my code will eventually go away without having to take it to the dealer for a ECU reset. Thanks
How often we overlook the basics of automotive engineering design. These are great videos. Keep up the good work!
I'd test a fuel pump with a pressure gauge. Observe fuel pressure while driving up a long hill. This loads the fuel system and demands max fuel flow. Typically a bad fuel pump the fuel pressure will drop under load and you can verify by watching the fuel pressure gauge. GM dealerships have a wired transducer pressure gauge where you can drive the vehicle with the gauge readout in the car seeing it's electronic. I've seen techs tape a fuel gauge to the windshield during the diagnosis test drive. No pressure drop under load eliminates the fuel pump as an issue.
I just can't say other than how extraordinary your videos are. I'm not a mechanic (software engineer actually) but I do have the passion for mechanic. Keep doing stuff like this!!!!
Thanks very much!!! I like people with passion for learning! I have it too!
So I got a 1999 Grand Am 2.4L 4 cyl. I know i have a bad converter, and I am getting a converter efficiency code, and it's on my list when budget allows. The converter code is the only code I am getting. The converter is fried due to bad coil back and the car being driven 20 miles with 2 cylinders not firing with raw fuel going into the exhaust and the converter was red hot. I can bang on the converter and hear the honeycomb rattling around inside. I am seeing a rich condition (Negative LTFT of about 15-19, STFT 0) at idle and experiencing a rough and low idle and exhaust smells rich at idle. I am noticing worse fuel mileage as well. As RPM increases STFT comes positive until LTFT comes to 0. I am thinking I may have a bad (leaky) injector, but how do I diagnose which one. I have a ample supply of junk yard parts at my disposal. So I am thinking of testing fuel pressure, checking fuel pressure regulator and then trying to swap one injector at a time. Is there a way to easily tell which injector might be leaky. Also should I wait and replace the converter which I know is bad first before doing anything. This problem with the idle and fuel mileage did exist before the coil pack incident that fried the converter. My understanding is the first O2 sensor at the manifold is reading the fuel mixture and adjusting fuel trims and the one after the converter is just verifying that the converter is working properly. If that is right I wouldn't think the bad converter would cause the fuel trim problems.
Very educational, and interesting information. It really add to the logic of troubleshooting. Thank you.
You sir are a great instructor! If you dont already,you could charge people to share your knowledge with them. I learned quite a lot from these videos. Thanks for uploading them!
Thanks bro. I actually do get paid pretty for this. even though it's just a hobby.
Gem of videos. Now programmed in my brain for fuel trim diagnostics. Thank you!
Nick P.
I learn many thing from this video. this information very valuable .can you help me to find service manual for Mercedes W202 C180 model 1999
wow,what a perfect explanation, everything was so clear,thanx for sharing with the people all your knowledge, and please keep the good job up.
You won't see this in a user manual for a handheld diagnostic tool. But you should watch this if you want to know how to use a handheld diagnostic tool.
Thanks so much for the tutorial! The concept of the fuel trip became much clearer after watching your videos. It also helped me narrow down the issues with the P0171 code to a MAF sensor rather than guessing and trying other possible causes.
Hi what's best cheap Digital Oscilloscope you recommend it? The ( FNIRSI 5012H Digital Oscilloscope Single-Channel 500 MS/s 100 MHz ) its good or not let me know please
I really don’t know honestly. I only gave two- my vantage pro and my picoscope. the vantage pro was certainly cheaper and works for 98% of what I do.
wow, excellent explanation on STFT and LTFT, appreciate the technique involved in this video, I finally understand, great job