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.
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
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.
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
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.
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.
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!!
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".
There is absolutely no-one else on RUclips who can explain concepts like this guy. Every single video is a winner. Unparalleled knowledge - unbeatable!
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.
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!!!!!!!
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.
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!
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.
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 .
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.
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.
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
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👍
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.
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.
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.
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 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!
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.
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.
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.
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
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!
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.
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.
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 ! 💡🔑🏹🎯🙌🏼
I see clearly now that every mechanic that I've worked with is an under-educated imposter. None of them knew anything about fuel trim and clearly thought it was useless info. You have provided incredibly helpful info. Thank you.
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.
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!
This is the ONLY explanation I've seen. It's good when the "teacher" actually cares about the subject matter. I can't wait to read my STFT and LTFT tomorrow! (Probably a MAF issue...but possibly a vacuum leak based on what I've learned from here). Now I have more confidence in dealing with it, at least.
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.
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.
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.
So much better/clearer explanation than all the other inferior videos out there. Even a backyard mechanic like me can tell when something makes sense as opposed to confusing unreliable information.
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 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.
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.
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.
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.
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.
Just now finding your channel, was actually trying to find legitimate diagnosis studys to help me as a technician. Ive hit a gold mine. Your channel has helped me tremendously already. I dont want to be a parts changer anymore
I'm a long term shade tree with a very tech background. Process control, SCADA, IT, etc. Always wanted to understand the mystery of fuel trim. Now I do. Thank you! Excellent presentation.
@SchrodingersBox Absolutely. Helps to understand Open Loop, Closed, Current Loop, Constant Voltage, etc. Done a lot of work w milli-amp sensors, Oscilloscopes, Data Acquisition & visually representing data with Graphical User Interfaces (GUI's). Really appreciated your plain language explanations & plan to check out your other vids.
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 RUclips. I wish to see more video.
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.
I must have watched this first 5-10 years ago, and when I had an issue with my vehicle, I immediately thought of these fuel trim videos, to rewatch them.
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.
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.
This is the third time I’ve watched this. So great. I took notes in my mechanic notebook. Can’t wait to go diagnose the Trooper and check on it’s fuel trims. THANKS FOR THIS. BEST VIDEO ON MECHANICAL DIAGNOSIS ON RUclips!
My dad was a hot rod mechanic back in the 50's and 60's. My mom always complained that when they went out on dates, he would literally pull over every few miles, pop the hood, and re-adjust the carburetor until it was perfect again. Drove her CRAZY!! 😂 Now we have computers that do that for us on-the-fly as we drive. Although I knew almost by heart most of the sections of this video series, I was missing some things that linked them together. Invaluable video series for us who obsess over correct diagnosis. Thanks Dad for the OCD, and thanks Matt, for your gift at teaching us. 🤘
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
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!
I cannot recommended these two videos enough. If you need to know about fuel trims - and you do - you'll not find a better tutorial anywhere on RUclips. It may take two or three viewings to pin it down, but your patience will be rewarded with an abundance of automotive diagnostic knowledge.
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
20:13 ahhh you forgot to erase that dot! Great videos man, nobody can explain this stuff as well as you can. I believe I'm having fuel delivery issues and your videos finally confirmed by suspicions to at least give me some direction. Mesmerized! Great teaching!!
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.
Just found your videos on a Lexus forum and I have to say I am so happy I did. The way you explained all of this has been a wonderful learning experience. I am having trouble with my wife's Lexus and now I can use this knowledge to get a better direction. Thank you so very much. You had saved me hours of headache. Have a wonderful day. Ken.
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.
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.
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!
Absolutely brilliant and clear explanation of fuel trims (not to mention your other videos). No BS, just clear facts with good troubleshooting questions made to test knowledge. This felt more like a college lecture with the quality of delivery. You've definitely earned yourself a new subscriber.
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 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
2 am on a Wednesday. Found this channel for the first time a few hours ago. It's going to be a rough day tomorrow due to binge watching Schrodinger's Box! THANKS!
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
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
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!!!
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.
You have absolutely helped more people than you could ever know!
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.
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
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.
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!!
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".
There is absolutely no-one else on RUclips 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'm a certified mechanic with 20 years experience and I enjoyed watching this video very much detailed and very accurate great job
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.
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!
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.
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!
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.
I can never thank you enough. I learn so much from you compared to other videos I watch.
Glad to hear!!
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 .
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
Fantastic videos you are a first class teacher ...thank you
you have a good way to explain
This was very generous of you to educate us on fuel trims to help us diagnose our car problems.
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👍
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.
Probably the best lecture I had. This hour is worth my 5 years in engineering school. Very well said. Respect
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.
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.
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 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!
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.
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.
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.
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'm a licensed automotive tech and this is amazing brush up on some things I've forgotten thanks for it.
Single most set of informative and educational videos I've ever studied. Thank you. I've had a massive paradigm shift.
Wonderfully eloquent comment!!
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!
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
After all these years I finally understand what fuel trim means. Thanks for the excellent video.
You sir are a saviour to us DIY guys with your thorough explanation of this type of diagnosis. Thank you so much.
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.
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 !
💡🔑🏹🎯🙌🏼
I see clearly now that every mechanic that I've worked with is an under-educated imposter.
None of them knew anything about fuel trim and clearly thought it was useless info.
You have provided incredibly helpful info.
Thank you.
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.
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!
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!
This is by far the best explanation of fuel trims I have seen. Thanks.
This is the ONLY explanation I've seen. It's good when the "teacher" actually cares about the subject matter. I can't wait to read my STFT and LTFT tomorrow! (Probably a MAF issue...but possibly a vacuum leak based on what I've learned from here).
Now I have more confidence in dealing with it, at least.
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.
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.
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.
So much better/clearer explanation than all the other inferior videos out there. Even a backyard mechanic like me can tell when something makes sense as opposed to confusing unreliable information.
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!
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.
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.
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.
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.
you explained it better than anyone else.
I've been looking for that for a long time. THANK YOU
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.
Just now finding your channel, was actually trying to find legitimate diagnosis studys to help me as a technician. Ive hit a gold mine. Your channel has helped me tremendously already. I dont want to be a parts changer anymore
So glad to hear that!!! Keep it up!!! You will be crazy successful in your field the more you can do this!!!
I'm a long term shade tree with a very tech background. Process control, SCADA, IT, etc. Always wanted to understand the mystery of fuel trim. Now I do. Thank you! Excellent presentation.
Glad to hear. The tech background does help that’s for sure.
@SchrodingersBox Absolutely. Helps to understand Open Loop, Closed, Current Loop, Constant Voltage, etc. Done a lot of work w milli-amp sensors, Oscilloscopes, Data Acquisition & visually representing data with Graphical User Interfaces (GUI's). Really appreciated your plain language explanations & plan to check out your other vids.
You're awesome! Thank you so much for taking the time to do this. Your teaching abilities are master level. Bless You!
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 RUclips. I wish to see more video.
+Asif Ali Wow thanks man! made my week!!!
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.
I must have watched this first 5-10 years ago, and when I had an issue with my vehicle, I immediately thought of these fuel trim videos, to rewatch them.
Yes they are still relevant!! I really need to update it for air fuel sensor as opposed to O2 sensors though.
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.
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.
One of the most educational car diagnostic videos I’ve ever come across. Thanks for uploading.
Wow, thanks!
This is the third time I’ve watched this. So great. I took notes in my mechanic notebook. Can’t wait to go diagnose the Trooper and check on it’s fuel trims. THANKS FOR THIS. BEST VIDEO ON MECHANICAL DIAGNOSIS ON RUclips!
Thanks man!!
Schrodingers Box where’s the paid channel I want in ??????
@@ktcgarage8572 www.schrodingersboxqm.com
Ive been wanting to solidify my knowledge on this subject for some time. This is very informative video. Just wow
You should have been a detective with your forensic analysis of car problems, Mr. Holmes. Good job.
I don't hit 'like' on many videos, but when I do... They are well explained and well thought out videos like these. Thank you for taking the time.
My dad was a hot rod mechanic back in the 50's and 60's. My mom always complained that when they went out on dates, he would literally pull over every few miles, pop the hood, and re-adjust the carburetor until it was perfect again. Drove her CRAZY!! 😂 Now we have computers that do that for us on-the-fly as we drive. Although I knew almost by heart most of the sections of this video series, I was missing some things that linked them together. Invaluable video series for us who obsess over correct diagnosis. Thanks Dad for the OCD, and thanks Matt, for your gift at teaching us. 🤘
Hahahahaha I remember those days!!!!
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
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!
Very good explanation of Fuel trim and how to use it for diagnostics. Thanks for posting this.
I cannot recommended these two videos enough. If you need to know about fuel trims - and you do - you'll not find a better tutorial anywhere on RUclips. It may take two or three viewings to pin it down, but your patience will be rewarded with an abundance of automotive diagnostic knowledge.
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
20:13 ahhh you forgot to erase that dot! Great videos man, nobody can explain this stuff as well as you can. I believe I'm having fuel delivery issues and your videos finally confirmed by suspicions to at least give me some direction. Mesmerized! Great teaching!!
I hardly make comments on videos, but I can't help saying that you're an amazing teacher. Thank you sir!
Wow, thank you!
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,
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.
I'm glad I watched both Pt1 and 2 just brill, although I will be recapping. Thanks Matt just brill.
Just found your videos on a Lexus forum and I have to say I am so happy I did. The way you explained all of this has been a wonderful learning experience. I am having trouble with my wife's Lexus and now I can use this knowledge to get a better direction. Thank you so very much. You had saved me hours of headache. Have a wonderful day. Ken.
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.
Many thanks from EGYPT brother , you are really know what you are doing , keep it up .
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!!
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.
Absolutely brilliant and clear explanation of fuel trims (not to mention your other videos). No BS, just clear facts with good troubleshooting questions made to test knowledge. This felt more like a college lecture with the quality of delivery.
You've definitely earned yourself a new subscriber.
Glad you enjoyed it!
These were super informative and the orderly scientific approach is great.
Thanks!
You're a natural at this! Thanks for sharing your knowledge.
Thank you. This has been the most informative video I'd seen. Quality is amazing. Clear and Eloquent explanation.
DAMN, Schro! This 10 year old video covered several engine diagnostics!!! Brilliant!!!
Triple GOLD! 😁
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 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
2 am on a Wednesday. Found this channel for the first time a few hours ago. It's going to be a rough day tomorrow due to binge watching Schrodinger's Box! THANKS!
Welcome aboard!
I have never REALLY understood STFT AND LTFT until watching this video. I hope my $100 scan tool shows me this information. Thanks for a great video
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
What the manual of the OBD-II could not explain.
I would like to give my second thumb here too.
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
it's good to watch a tutorial like this one on a regular basis to keep from forgetting the info.