I followed up on the vid where you encouraged viewers to learn more about fuel trim and I ended up at this excellent vid. Thanks to this excellent vid and your encouragement I understand much more about keeping the modern engine running.
always a pleasure learning, when its very well orchestrated, I speak for most when i say, "We aprecate your hard work, putting these videos out", Thank You!
My STFT is behaving as expected when idling in closed loop, by hunting around 0.0%, plus or minus 3%. However the LTFT is stuck on -10.2% A quick blip of the throttle at it changes to -9.4% RPM flucturating 796 to 803 rpm MAP fluctuates around 25kPa 02s1 fluctuates around 0.00mA. plus 0 to minus 0.07mA 02s2 fluctates 0.57V to 0.63V If go from idle to holding the throttle at 2000rpm or 3000rpm. The STFT behaves as expected. But the LTFT is still in minus figures but closer to 0% higher the rpm
Looked at a number of Videos and this was really a good one. The animations were very beneficial. Thanks so very much. Hoping now I have a better comprehension of why I have a 19.5 Long term reading on bank 1 and only a 2,5 on bank 2 after replacing all four o2 sensors. I have a 2004 JaguarXJ8 4.2 with 91,000 miles I enjoy driving but have a problem with PO171 and Restricted performance since March. Thanks for the video. Great Job.
That is, unless the customer has cleared codes... Then ur F'd, as clearing codes resets the tables. Otherwise, yea, you can look at FTs in conjuction with codes and misfire counters all together in a package diagnosis...
The pisson chamber? took me a while, lol; STOY - KIO- metric ...E X C E L L E N T video,thanks. added: E X C E L L E N T VIDEO, you know a great deal!!!
Very interesting video! Have a question. On my 10 year old vehicle at idle, STFT is around +6% and LTFT is shown at +3%(lower at times). When I increase RPM, I notice that STFT drops a bit to maybe +3 or less. While driving LTFT may go to +2 or less. I have checked hoses around the engine and cleaned MAF and looked at throttle body and all is clean and hoses attached properly and in very good shape. Housing of the PCV valve looks clean. I also do have bank 2 data which I haven't looked at yet. I don't think I need to bother with anything, but out of curiosity what would you suggest?
What was your main Symptom? This sounds very similar to what is happening to my vechicle in my Symptom is an extra 26% usage in Fuel. Also no CEL was triggered.
@@Charkatak Thanks for replying, I'm still trying to track what the issue is. I've seen some anecdotal posts, about how others are getting worse fuel economy and I am wondering here in Canada if they somehow upped the ethanol content.
@@anteka12 Usually when ethanol is increased, gas stations should post information or a sticker telling the percentage. Have you tried to calculate a fuel real usage after refueling? Anything in oxygen sensor data?
Hey Kirby what Matt was trying to get to and I don't think he specifically said it with this words. It is possible for a person to hold the belief that God doesn't exist but he might exist. Same as believing Jenna is not an Ax Murderer but she might or could be, as in it is possible. Because they are different propositions.
How does this get my 89 s10 pickup with a manual transmission running right? I have replaced everything but the tps and map sensor. I live near Harrisburg Pa and I the morning I can drive for about 15 minutes and the engine runs great for a truck that's 30 years old. Then like a switch was flipped the engine starts to run like crap. When I put the clutch in the engine tries to die and some times it does. The engine shakes violently and I almost didn't make it home today. When it does this why can't the driver give the ecm an error and tell it to run. Don't understand how the ecm can't tell the engine is shaking and do something to correct the issue? U unplugged the o2 sensor hoping to keep it in open loop. But 15 minutes later engine is running like crap. I firmly believe that when a engineer retires they are NOT done working they get to work in repairing the garbage they designed. I thought I would learn something here but I have no clue what you are talking about. This is why I don't do this professionally any more. Stupid engineers messing stuff up designing dumb crap.
strange. I thought Load would be a function of RPM and Speed. But they graph RPM and Load. I thought it would be simpler to just graph Load and Fuel Trim.
How does this get my 89 s10 pickup with a manual transmission running right? I have replaced everything but the tps and map sensor. I live near Harrisburg Pa and I the morning I can drive for about 15 minutes and the engine runs great for a truck that's 30 years old. Then like a switch was flipped the engine starts to run like crap. When I put the clutch in the engine tries to die and some times it does. The engine shakes violently and I almost didn't make it home today. When it does this why can't the driver give the ecm an error and tell it to run. Don't understand how the ecm can't tell the engine is shaking and do something to correct the issue? U unplugged the o2 sensor hoping to keep it in open loop. But 15 minutes later engine is running like crap. I firmly believe that when a engineer retires they are NOT done working they get to work in repairing the garbage they designed. I thought I would learn something here but I have no clue what you are talking about. This is why I don't do this professionally any more. Stupid engineers messing stuff up designing dumb crap.
I bet if you tested a brand new car the LTFT wouldn't be zero. In fact if you buy a new car the first thing to do is find the current LTFT, so you know how much you change as the car ages.
So to LTFT First because it comes to "action" due to an Overtake over a 10% "correction" of the STFT. Did I get it Right sir? Thank You. ( I unite to spelunkard in Wellcome)
Forgot to mention this is a 2010 elantra with only 62,000 kms. I did clean the IAC idle control valve, Map, TPS sensor. Car has been restarted at least 50 times since these sensore were cleaned.
these 02 sensors are failure of logic . short term blue is like constantly trying to avoid problem as result creating even more problems . can you disconnect that short term pre cat o2 it brings to 0% . just let the long term or after cat 02 do the job . ?
Excellent informative video but to prove your point can you please make video of actual case study of LTFT to show what was creating the problem and how you solve it when you came across actual vehicle please.
Can you tell me what I need to do! I have a rough idle on cold starts for about 15 sec then idles better than worse again, after it comes to operating temperature. The idle is rough with a load on the engine at stand still or going up hill. I have no check engine light or saved codes. Gas mileage and performance is poor. the long term LTFT is - 4.7 and the STFT is -0.3 What do these numbers mean. What should I be looking for? I have a scanner? Thanks
Yes, however the PCM does not read LTFDT as a stand alone input. Instead it reads them as a combined input. So, if STFT is at 10% and LTFT is at 5% the total would be 15% and that will seta code
awesome! I got a high negative LTFT hitting -9% on both banks especially on idle and feel like some under power, LTFT returns close to zero when revving up engine. I check the fuel rail pressure, it's within normal range (DI engine). no blocked PCV. No missing fire detected on scanner. I'm completely lost. side note: when I unplug the IAT sensor, seems engine runs better with happier throttle response and more power.
More info is needed to make any assessment. Are those numbers at idle, and how do they respond above idle, at wide open throttlele, etc. ? How do they respond when you add extra air and/or extra fuel. Those are the things you need to be checking because anything less would just be a guess
@@realfixesrealfast this was over a 20 mile drive, it records maximum and minimum values over the driving time, long term seems to settle around 4 or 5, short term can be okay but sometimes gives plus 25.
Ninosinamor19 If the spark plug hole in the cylinder head is stripped out, you'll need to drill out the hole to a larger diameter, tap it, and install replacement threads.
My ltft has an error, al the time it is 0.78. I know when it was working ok it was 5 to -7. My exhaust pipe is now black, also fuel consumption has increased. Is there a way to reset it? I have tried battery removal for 24h and no succes. Also, there are no error codes , O2 sensor is working as it should, stft fallows O2 sensor.
both SFTF & LTFT are computer "responses" not "controls" , so no there is no reset for them. It would take some accurate hands on evaluation of them to determine the issue.
@@realfixesrealfast would it be correct to says that when every thing are working correctly the car's exhaust would be having slightly excess O2 of 2% vs 21% of O2 in the air. Yes, no?. Y I bought a 2006 Mercedes and put in plug & dashboard display OBD2. While driving O2 sensor reading fluctuates between 0.65 to 0.8V. This short profile of V swinging value, I understood, is only for cars made before 2007 which uses different soft ware for O2 sensor self check. It does only drop to 0.1V briefly when braking to stop. Left on cruise mode the short fuel trim value changes slightly and does not swing about too much. Long fuel trim value hardly moves and would be moved by 2% or less. Thank you and have a nice day.
@@whlawson5812 from what you explain I would say Yes. Some may argue that perfect is 0% but there are just too many variables with 2006 that has several miles on it. I think you are ok
if you charge engine to 3000~3500RPM and the value of LTFT down, is probably vacuum problem, if not, maybe fuel injector (or any fuel sysem, like fuel pump, filter...) has a problem.
@@teive at idle i got 3% only for LTFT, but if I run it fluctuates to 5% upto 12% I check the fuel pressure is normal I tried fuel injector cleaner and still the LTFT is about that value, i changed the fuel filter check it improves a bit. But is flactuates to those values.
and STFT, is normal -3%~3%? This value of 12% on LTFT is positive (+), right? If is positive, the PCM need to send more fuel to system. How many cylinder has your car?
Enjoy! Not really, if you do your own work/diagnostics on newer cars, you really need to understand these types of tests. Otherwise you are paying someone else to do these tests at a premium.
You don't mess with the programming. If LTFT is adding or removing fuel, it means there is a persistent condition. You then look at what is causing the condition. Such as if LTFT is adding fuel, you look for unmetered air getting in or the amount of actual fuel being injected is not as much as the computer believes is being added based on injector on-time and fuel system pressure.
I agree. FT's are the first data PIDs I glance at when scanning through engine data. Good explanation Duane. Remember the days of block learn :)
Block learn, haven't seen that in a while lol
👍 👍
And "Integrator".
I followed up on the vid where you encouraged viewers to learn more about fuel trim and I ended up at this excellent vid. Thanks to this excellent vid and your encouragement I understand much more about keeping the modern engine running.
Well explained and presented. I'm a DIYer. This will help a whole lot in trying to understand why MILs are triggered. Well done sir.
always a pleasure learning, when its very well orchestrated, I speak for most when i say,
"We aprecate your hard work, putting these videos out",
Thank You!
As always, excellent, clear explanation.
Great to have you back and i hope you're well.
Kind regards, Joe
Great explanation Dwayne on the importance of checking long term fuel trim numbers.
Wonderful video. Watched many video's on the subject, but yours finally explains why we should adopt this approach to diagnostics. Makes sense.
What a pleasure to listen to such a precise and edifying video. Thank you
Excellent teaching techniques !
Great video, very informative! I always check fuel trim when diagnosing a drivability concern.
Well done explanation! I loved the use of graphics and the way you described it. Thank you for this video
My STFT is behaving as expected when idling in closed loop, by hunting around 0.0%, plus or minus 3%.
However the LTFT is stuck on -10.2% A quick blip of the throttle at it changes to -9.4%
RPM flucturating 796 to 803 rpm
MAP fluctuates around 25kPa
02s1 fluctuates around 0.00mA. plus 0 to minus 0.07mA
02s2 fluctates 0.57V to 0.63V
If go from idle to holding the throttle at 2000rpm or 3000rpm. The STFT behaves as expected. But the LTFT is still in minus figures but closer to 0% higher the rpm
Looked at a number of Videos and this was really a good one. The animations were very beneficial. Thanks so very much. Hoping now I have a better comprehension of why I have a 19.5 Long term reading on bank 1 and only a 2,5 on bank 2 after replacing all four o2 sensors. I have a 2004 JaguarXJ8 4.2 with 91,000 miles I enjoy driving but have a problem with PO171 and Restricted performance since March. Thanks for the video. Great Job.
OK what are you on Bank 2 short term fuel trim is fluctuating at 3% but on Bank 2 long term fuel trim is fluctuating between 14% and 15%
This is an awesome and informative video for me, a DIYer. Clear concise and understandable. Thank you so much!
Thank you for sharing your knowledge 😃
My LTFT is +18%, my STFT is subtracting between 2%and 10.5%. What gives?
Great video ! Excellent explanation and graphics . thank you for taking your time to post this.
very well explained,thanks Duane ;- ]
That is, unless the customer has cleared codes... Then ur F'd, as clearing codes resets the tables.
Otherwise, yea, you can look at FTs in conjuction with codes and misfire counters all together in a package diagnosis...
Nice to have you back, Duane!
spelunkerd your channel is great too.
The pisson chamber? took me a while, lol; STOY - KIO- metric
...E X C E L L E N T video,thanks.
added: E X C E L L E N T VIDEO, you know a great deal!!!
I have both short trim bank 1 25.0 and Short trim bank 2 25.0 they both goes back down to 0.0 then go back up to 25.0 what could this be
My 4runner has a 38% positive LTFT P0171
Awesomeness
What if there is a difference between bank 1 and 2
Bank 1 is 8.6% and bank 2 is 4.7%
Is it write or wrong
Thank you for sharing your knowledge
good video. would have been better with an example at
the end
I really love the way you explain your videos congrats!!!
When am speeding my ltft and stft is at 0. As soon as i make a stop or even take my foot off the gas my ltft is at +14.8.
Excellent explanation. Easy to understand. Thank You 🙄
Very clear and understandable explanation. Bravo on a great presentation.
Brilliant Teacher
I certainly learned more about fuel trims from this video ! Thanks !
Glad it helped, thanks for your comments.
Very interesting video! Have a question. On my 10 year old vehicle at idle, STFT is around +6% and LTFT is shown at +3%(lower at times). When I increase RPM, I notice that STFT drops a bit to maybe +3 or less. While driving LTFT may go to +2 or less. I have checked hoses around the engine and cleaned MAF and looked at throttle body and all is clean and hoses attached properly and in very good shape. Housing of the PCV valve looks clean. I also do have bank 2 data which I haven't looked at yet. I don't think I need to bother with anything, but out of curiosity what would you suggest?
From what you have said, I think you are fine. To suspect a problem you would need to see the STFT & LTFT combined value consistently going above 10%,
What was your main Symptom? This sounds very similar to what is happening to my vechicle in my Symptom is an extra 26% usage in Fuel. Also no CEL was triggered.
@@anteka12 No symptoms, just wish to have better fuel economy and thought fuel trims could be improved.
@@Charkatak Thanks for replying, I'm still trying to track what the issue is. I've seen some anecdotal posts, about how others are getting worse fuel economy and I am wondering here in Canada if they somehow upped the ethanol content.
@@anteka12 Usually when ethanol is increased, gas stations should post information or a sticker telling the percentage. Have you tried to calculate a fuel real usage after refueling? Anything in oxygen sensor data?
This was extremely helpful for redirecting focus when trying to figure out why is my car rich or why is it lean. Very helpful!
Very informative video!!
I just love this video explanation.
thanks a ton !
Hey Kirby what Matt was trying to get to and I don't think he specifically said it with this words. It is possible for a person to hold the belief that God doesn't exist but he might exist. Same as believing Jenna is not an Ax Murderer but she might or could be, as in it is possible. Because they are different propositions.
Interesting, thanks so much
How does this get my 89 s10 pickup with a manual transmission running right? I have replaced everything but the tps and map sensor. I live near Harrisburg Pa and I the morning I can drive for about 15 minutes and the engine runs great for a truck that's 30 years old. Then like a switch was flipped the engine starts to run like crap. When I put the clutch in the engine tries to die and some times it does. The engine shakes violently and I almost didn't make it home today. When it does this why can't the driver give the ecm an error and tell it to run. Don't understand how the ecm can't tell the engine is shaking and do something to correct the issue? U unplugged the o2 sensor hoping to keep it in open loop. But 15 minutes later engine is running like crap. I firmly believe that when a engineer retires they are NOT done working they get to work in repairing the garbage they designed. I thought I would learn something here but I have no clue what you are talking about. This is why I don't do this professionally any more. Stupid engineers messing stuff up designing dumb crap.
strange. I thought Load would be a function of RPM and Speed. But they graph RPM and Load. I thought it would be simpler to just graph Load and Fuel Trim.
How does this get my 89 s10 pickup with a manual transmission running right? I have replaced everything but the tps and map sensor. I live near Harrisburg Pa and I the morning I can drive for about 15 minutes and the engine runs great for a truck that's 30 years old. Then like a switch was flipped the engine starts to run like crap. When I put the clutch in the engine tries to die and some times it does. The engine shakes violently and I almost didn't make it home today. When it does this why can't the driver give the ecm an error and tell it to run. Don't understand how the ecm can't tell the engine is shaking and do something to correct the issue? U unplugged the o2 sensor hoping to keep it in open loop. But 15 minutes later engine is running like crap. I firmly believe that when a engineer retires they are NOT done working they get to work in repairing the garbage they designed. I thought I would learn something here but I have no clue what you are talking about. This is why I don't do this professionally any more. Stupid engineers messing stuff up designing dumb crap.
Great video!
I bet if you tested a brand new car the LTFT wouldn't be zero. In fact if you buy a new car the first thing to do is find the current LTFT, so you know how much you change as the car ages.
My LTFT range between -8 and -13 percent. What prob my car probably has?
So to LTFT First because it comes to "action" due to an Overtake over a 10% "correction" of the STFT. Did I get it Right sir?
Thank You.
( I unite to spelunkard in Wellcome)
Excellent educational video, well done.
Forgot to mention this is a 2010 elantra with only 62,000 kms. I did clean the IAC idle control valve, Map, TPS sensor. Car has been restarted at least 50 times since these sensore were cleaned.
these 02 sensors are failure of logic . short term blue is like constantly trying to avoid problem as result creating even more problems . can you disconnect that short term pre cat o2 it brings to 0% . just let the long term or after cat 02 do the job . ?
Excellent informative video but to prove your point can you please make video of actual case study of LTFT to show what was creating the problem and how you solve it when you came across actual vehicle please.
Muchas Gracias... Great explanation... Cheers.. Daniel
its obvious thinking for those who know and understand these fuel trims!
I was having 15 minutes to waste. So I wasted this 15 minutes, thankyou.
It's Stoli-o-metric! Make that a double...
Simple and accurate explaination but highly intelligent
awesome
thank you for taking your time to make this video. it was helpful
So which sensor calculates the long term fuel trims?
Can you tell me what I need to do! I have a rough idle on cold starts for about 15 sec then idles better than worse again, after it comes to operating temperature. The idle is rough with a load on the engine at stand still or going up hill. I have no check engine light or saved codes. Gas mileage and performance is poor. the long term LTFT is - 4.7 and the STFT is -0.3 What do these numbers mean. What should I be looking for? I have a scanner? Thanks
Your car is adding fuel mean that you have a vacuum leak somewhere.
👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍100%
You mentioned that -10% to +10 STFT is normal. Does the same rule of thumb apply for the LTFT?
Yes, however the PCM does not read LTFDT as a stand alone input. Instead it reads them as a combined input. So, if STFT is at 10% and LTFT is at 5% the total would be 15% and that will seta code
awesome! I got a high negative LTFT hitting -9% on both banks especially on idle and feel like some under power, LTFT returns close to zero when revving up engine. I check the fuel rail pressure, it's within normal range (DI engine). no blocked PCV. No missing fire detected on scanner. I'm completely lost. side note: when I unplug the IAT sensor, seems engine runs better with happier throttle response and more power.
U ever find out issues?
You're running rich on both banks...could be MAF over-reporting amount of air coming in
how to get rid of p0133 code on a 98 volvo v70
Excelent explanation thank u great videos
More than perfect 👌🏻 👍🏻👍🏻👍🏻
Love your repair videos, Duane!
I have a short term fuel trim of maximum + 25 while long term fuel trim is at 4.7% what should I be looking for, vacuum leak?
More info is needed to make any assessment. Are those numbers at idle, and how do they respond above idle, at wide open throttlele, etc. ? How do they respond when you add extra air and/or extra fuel. Those are the things you need to be checking because anything less would just be a guess
@@realfixesrealfast this was over a 20 mile drive, it records maximum and minimum values over the driving time, long term seems to settle around 4 or 5, short term can be okay but sometimes gives plus 25.
I have a cuestión how can I fix it one spark plug has a swept thread.?
Ninosinamor19 If the spark plug hole in the cylinder head is stripped out, you'll need to drill out the hole to a larger diameter, tap it, and install replacement threads.
Thanks man for the perfect explanation .
My ltft has an error, al the time it is 0.78. I know when it was working ok it was 5 to -7. My exhaust pipe is now black, also fuel consumption has increased.
Is there a way to reset it?
I have tried battery removal for 24h and no succes. Also, there are no error codes , O2 sensor is working as it should, stft fallows O2 sensor.
both SFTF & LTFT are computer "responses" not "controls" , so no there is no reset for them. It would take some accurate hands on evaluation of them to determine the issue.
@@realfixesrealfast would it be correct to says that when every thing are working correctly the car's exhaust would be having slightly excess O2 of 2% vs 21% of O2 in the air. Yes, no?. Y
I bought a 2006 Mercedes and put in plug & dashboard display OBD2. While driving O2 sensor reading fluctuates between 0.65 to 0.8V. This short profile of V swinging value, I understood, is only for cars made before 2007 which uses different soft ware for O2 sensor self check.
It does only drop to 0.1V briefly when braking to stop. Left on cruise mode the short fuel trim value changes slightly and does not swing about too much. Long fuel trim value hardly moves and would be moved by 2% or less.
Thank you and have a nice day.
@@whlawson5812 from what you explain I would say Yes. Some may argue that perfect is 0% but there are just too many variables with 2006 that has several miles on it.
I think you are ok
That was BriLL.!
very good explanation 👍
good info as always. thank you for sharing.
Fantastic explanation thanks
SWEEET VID MAN , THANK YOU 👍 👍
Lol truth
Excellent.
Thank you sir. Regards.
finally !!!!! you are back
Excellent, Thanks!
thanks you
my car long term fuel trim is 10% - 12% while my car is running is this normal or there is a problem with me vacuum or fuel system??thank u
if you charge engine to 3000~3500RPM and the value of LTFT down, is probably vacuum problem, if not, maybe fuel injector (or any fuel sysem, like fuel pump, filter...) has a problem.
@@teive at idle i got 3% only for LTFT, but if I run it fluctuates to 5% upto 12% I check the fuel pressure is normal I tried fuel injector cleaner and still the LTFT is about that value, i changed the fuel filter check it improves a bit. But is flactuates to those values.
and STFT, is normal -3%~3%? This value of 12% on LTFT is positive (+), right? If is positive, the PCM need to send more fuel to system. How many cylinder has your car?
@@teive 4 cylinder, 2.2l ecotec, 3% is positive and while running is going up to 10-12% +.
try to log STFT data, maybe O2 sensor need to be replaced. Well, good lucky on your diagnostic. Regards, my friend.
Does a high negative LTFT means the engine is not running on optimal power output?
High and negative ? Thats confusing
@@strokewarrior5762 LTFT = -21
Running rich. Mine is running at -22 at long term. Been trying to figure out what it could be.
@@Shotbymic_2 mine is -15 but it changes at full throttle to -9 . Does it mean injectors are leaky? What you think
@@amirouw mine is also -21. STFT is around 0
Great video. I really appreciate the way you explain this information.
It can't be explained as the way you did Sir. thank's a lot
Stoy! Stoy! Stoy! @5:56 STOI~CHIO~METRIC is
pronounced: [STOY~keo~metric]
......... [NOT: STO-e-o~ko~metric]
No one cares
The education in the video was more important than your pronunciation of the word
unless ur a programmer this is MUTE!
Enjoy! Not really, if you do your own work/diagnostics on newer cars, you really need to understand these types of tests. Otherwise you are paying someone else to do these tests at a premium.
You don't mess with the programming. If LTFT is adding or removing fuel, it means there is a persistent condition. You then look at what is causing the condition. Such as if LTFT is adding fuel, you look for unmetered air getting in or the amount of actual fuel being injected is not as much as the computer believes is being added based on injector on-time and fuel system pressure.
Every decent mechanic/technician should know this. So your comment is moot!