High negative fuel trims at idle
01-09-2015, 06:39 PM
#11
Yes, the old post is in the spoiler to organize the post a bit.
Only mod that isn't suspension related is the catback. No leaks found when spray testing it. Everything engine related is oem including my air filter replaced about ~1000 mi ago.
Only mod that isn't suspension related is the catback. No leaks found when spray testing it. Everything engine related is oem including my air filter replaced about ~1000 mi ago.
01-12-2015, 02:21 PM
#15
Sorry for the delay but I knew this would be a long post and take time.....
From your posts I will assume no hard code has been set. I have owned my car since 2001 and not a season goes by she scares the s*** out of me as I stop at a red light and the revs drop to the point of stalling....but Electra has never let me down (I.e. Stalled). This is normal. I assume you have had this experience and have now tried using your app and sending unit to understand it.
Let take a closer look at Fuel Trim. Starting with -"x" (negative) meaning x% reduction in fuel and "x" (positive) meaning x% increase in fuel. The range available is +/-100%. So your -10 is -10%.
Short Term Fuel Trim (STFT)
This trim is "volatile" and erased each time you turn the car off. STFT's job is to adjust fuel flow to achieve stoichiometry to 14:7(I.e. An air fuel ratio of 14 parts air to 7 parts fuel....considered optimal for combustion of fuel). the adjustment is made based on either what is stored as a start point in Long Term Fuel Trim ((LTFT) or the base map in the ECU (if the ECU is reset as you did).
Long Term Fuel Trim (LTFT)
This value varies over time and is adjusted with every running of the car. It is non-volatile and stored in the ECU (Keep Alive Memory or KAM for short). This learned value is stored until you disconnect the battery or reset LTFT with a PCM Scan Tool.
STFT is adjusted based on the voltages sent from the Primary O2 sensor. Decreasing voltages increase STFT. Increasing voltage decreases STFT. Many things can vary the O2 level. The two most common are air temp and elevation. So the temp drops and your car compares STFT and LTFT to make an adjustment to optimize stoichiometry. Sometimes this causes the RPM drop you note. The ECU holds the injector open (or closed) to "trim" the fuel. Over time the ECU gets sick of large % swings in STFT and adjusts the start point;LTFT. The two trims are compared based on an algorithm for what are known as adaptive limits. Both trims can compensate for lean or rich conditions to a point. If an "adaptive limit" is reached then the car will cry uncle and set a code.
From what I have read you have not hit that adaptive limit and are just learning about the annoying tolerance setting Honda Engineering put on the trim. Deal with it and move on unless the car stalls.
Utah
From your posts I will assume no hard code has been set. I have owned my car since 2001 and not a season goes by she scares the s*** out of me as I stop at a red light and the revs drop to the point of stalling....but Electra has never let me down (I.e. Stalled). This is normal. I assume you have had this experience and have now tried using your app and sending unit to understand it.
Let take a closer look at Fuel Trim. Starting with -"x" (negative) meaning x% reduction in fuel and "x" (positive) meaning x% increase in fuel. The range available is +/-100%. So your -10 is -10%.
Short Term Fuel Trim (STFT)
This trim is "volatile" and erased each time you turn the car off. STFT's job is to adjust fuel flow to achieve stoichiometry to 14:7(I.e. An air fuel ratio of 14 parts air to 7 parts fuel....considered optimal for combustion of fuel). the adjustment is made based on either what is stored as a start point in Long Term Fuel Trim ((LTFT) or the base map in the ECU (if the ECU is reset as you did).
Long Term Fuel Trim (LTFT)
This value varies over time and is adjusted with every running of the car. It is non-volatile and stored in the ECU (Keep Alive Memory or KAM for short). This learned value is stored until you disconnect the battery or reset LTFT with a PCM Scan Tool.
STFT is adjusted based on the voltages sent from the Primary O2 sensor. Decreasing voltages increase STFT. Increasing voltage decreases STFT. Many things can vary the O2 level. The two most common are air temp and elevation. So the temp drops and your car compares STFT and LTFT to make an adjustment to optimize stoichiometry. Sometimes this causes the RPM drop you note. The ECU holds the injector open (or closed) to "trim" the fuel. Over time the ECU gets sick of large % swings in STFT and adjusts the start point;LTFT. The two trims are compared based on an algorithm for what are known as adaptive limits. Both trims can compensate for lean or rich conditions to a point. If an "adaptive limit" is reached then the car will cry uncle and set a code.
From what I have read you have not hit that adaptive limit and are just learning about the annoying tolerance setting Honda Engineering put on the trim. Deal with it and move on unless the car stalls.
Utah
01-12-2015, 02:54 PM
#16
My car showed high fuel trims pulling fuel when I first logged it (MY2004). It had all the normal I/H/E stuff and the car had 28k miles. I assumed my modifications where causing the high fuel trims, so I then got ahold of a friend with a completely stock car with low mileage... Same fuel trims. I ended up using my Greddy to pull fuel at idle, however, I then had to compensate with temp corrections as it would straight sputter at idle when the engine got heat soaked at and AutoX.
Eventually I moved on to an AEM v2 so I could tune the car like I'm used to tuning... Full control. Not only did I solve this issue, but I got rid of the shudder/near stalling I would get when the car would come down to idle. I concluded it's the factory tuning, which I couldn't really do anything about with a 2004 without swapping ECU's.
I would consider STFT "reactive". If there is no correction being made (via perfect AFR or LTFT handling it), it disappears. At no point is it stored and is "erased" when there is nothing to correct.
And you're looking for 14.7:1. 14 parts air to 1 part fuel.
Eventually I moved on to an AEM v2 so I could tune the car like I'm used to tuning... Full control. Not only did I solve this issue, but I got rid of the shudder/near stalling I would get when the car would come down to idle. I concluded it's the factory tuning, which I couldn't really do anything about with a 2004 without swapping ECU's.
Let take a closer look at Fuel Trim. Starting with -"x" (negative) meaning x% reduction in fuel and "x" (positive) meaning x% increase in fuel. The range available is +/-100%. So your -10 is -10%.
Short Term Fuel Trim (STFT)
This trim is "volatile" and erased each time you turn the car off. STFT's job is to adjust fuel flow to achieve stoichiometry to 14:7(I.e. An air fuel ratio of 14 parts air to 7 parts fuel....considered optimal for combustion of fuel). the adjustment is made based on either what is stored as a start point in Long Term Fuel Trim ((LTFT) or the base map in the ECU (if the ECU is reset as you did).
Short Term Fuel Trim (STFT)
This trim is "volatile" and erased each time you turn the car off. STFT's job is to adjust fuel flow to achieve stoichiometry to 14:7(I.e. An air fuel ratio of 14 parts air to 7 parts fuel....considered optimal for combustion of fuel). the adjustment is made based on either what is stored as a start point in Long Term Fuel Trim ((LTFT) or the base map in the ECU (if the ECU is reset as you did).
And you're looking for 14.7:1. 14 parts air to 1 part fuel.
01-12-2015, 04:27 PM
#17
You are correct on the AFR. 14.7 Air to 1 part fuel is correct. My bad!,
Interesting observation on your car. I am using "Getting to Know OBD-II" by Birnbaum & Truglia (Ref:ISBN 0-9706711-0-5) as my source material. The material was written under the guidance of Arvon Mitcham; Lead Project Engineer, On-Board Diagnostics, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Certification and Compliance Division. They seem to have a different opinion of how the system works.
.
Perhaps it is the aftermarket ECU?
Utah
Interesting observation on your car. I am using "Getting to Know OBD-II" by Birnbaum & Truglia (Ref:ISBN 0-9706711-0-5) as my source material. The material was written under the guidance of Arvon Mitcham; Lead Project Engineer, On-Board Diagnostics, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Certification and Compliance Division. They seem to have a different opinion of how the system works.
.
Perhaps it is the aftermarket ECU?
Utah
01-12-2015, 05:20 PM
#18
So the only solution is to use a fully programmable engine management to basically correct the fueling table?!?!?!
The car didn't come like from the factory otherwise none of us would have bought this thing!
How can we restore the performance without resorting to aftermarket mapping??
The car didn't come like from the factory otherwise none of us would have bought this thing!
How can we restore the performance without resorting to aftermarket mapping??
01-12-2015, 10:07 PM
#19
Thanks for your replay Utah. My car has not thrown any CEL or codes, and I doubt it will because I think they only come on if LTFT reaches +/- 25 which I do not see too often on the STFTs besides the occasional spikes. I been trying to get some local people to let me see their logs to see just how common or uncommon this issue is. So far I was given only 1 other log and his car does not sit in the negative double digits at idle (STFT), though it does hit them occasionally in spikes.
My main worry is that I am ready to go boosted, but do not want to add all those things on and possibly just band-aid or mask an underlying problem.
gptoyz's friends car is having similar issues but I think his is even having an even worse time because I believe he mentioned his plugs were fouled when he pulled them. My spark plugs were in relatively good condition when I pulled them, which I assume is because the ecu is doing its job and pulling fuel when something is causing it to run rich.
On a side note..
If tuning is the only way to fix it, I have aem ems v2 ready to toss on.
My main worry is that I am ready to go boosted, but do not want to add all those things on and possibly just band-aid or mask an underlying problem.
gptoyz's friends car is having similar issues but I think his is even having an even worse time because I believe he mentioned his plugs were fouled when he pulled them. My spark plugs were in relatively good condition when I pulled them, which I assume is because the ecu is doing its job and pulling fuel when something is causing it to run rich.
On a side note..
If tuning is the only way to fix it, I have aem ems v2 ready to toss on.
01-13-2015, 05:04 AM
#20
You are correct on the AFR. 14.7 Air to 1 part fuel is correct. My bad!,
Interesting observation on your car. I am using "Getting to Know OBD-II" by Birnbaum & Truglia (Ref:ISBN 0-9706711-0-5) as my source material. The material was written under the guidance of Arvon Mitcham; Lead Project Engineer, On-Board Diagnostics, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Certification and Compliance Division. They seem to have a different opinion of how the system works.
.
Perhaps it is the aftermarket ECU?
Utah
Interesting observation on your car. I am using "Getting to Know OBD-II" by Birnbaum & Truglia (Ref:ISBN 0-9706711-0-5) as my source material. The material was written under the guidance of Arvon Mitcham; Lead Project Engineer, On-Board Diagnostics, U.S. Environmental Protection Agency, Office of Transportation and Air Quality, Certification and Compliance Division. They seem to have a different opinion of how the system works.
.
Perhaps it is the aftermarket ECU?
Utah
Short term fuel trims correct a problem as it is happening. If your AFR is drifting from stoich, STFT's are there to bring it back in check in real-time. If there is a big, constant trend, values will start being corrected by LTFT which should reflect in less STFT. So in reality, they'll "clear" when there is nothing to correct. With that said, AFR is never spot on 100% of the time as there will always be minor fluctuations.