Questions tagged [fuel-trims]
30 questions
23
votes
1 answer
LTFT and STFT values are off and don't make sense
Car is a 2015 BMW M5 and it has an aftermarket CAI and a catback (slip on) exhaust. No other performance mods or tunes.
About 6-7 months ago, I bought a Kiwi OBD-II reader, simply out of curiosity as I am a computer guy and a geek and was curious…
DerStig
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15
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1 answer
What exactly are fuel trims?
What is meant by the term "fuel trim"?
Why are they so important in diagnosing engine operation issues?
How do short-term fuel trims differ from long-term fuel trims?
Zaid
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12
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3 answers
Cold air intake causing rich condition
This is a follow up question to my initial question which can be found here : LTFT and STFT values are off and don't make sense
Car is a 2015 F10 M5
Mods : Cold air intake, aftermarket rear muffler (just section 3).
Since posting the initial…
DerStig
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9
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1 answer
P0171 and Fuel Trims
I have a 2002 Toyota Corolla (1zz-fe engine) and I am getting a P0171 code - lean condition. I am trying to make sense of my fuel trim values and I was hoping someone could help understand these results:
I am measuring on Neutral, after the engine…
Florent
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7
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2 answers
Exhaust Backpressure and Its Impact on LTFT Values
This is a follow-up from my initial question which can be found here : LTFT and STFT values are off and don't make sense.
Car : BMW 2015 F10 M5
Modifications : Eisenmann Race Catback Exhaust, MSR Cold Air Intake. Everything else stock.
The summary…
DerStig
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5
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1 answer
What does the ECU use the long term fuel trim for?
I have a 2001 Honda Prelude SH (Honda H22A4 engine). I was trying to determine how the reported short/long term fuel trims fit in to the fuel control loop (in particular I was wondering if the long term and short term values were added together to…
Jason C
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4
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Why does my LTFT1 make wilder, faster changes than STFT1?
[1999 4Runner, 6-cylinder 5VZ engine. Not supercharged.]
STFT1: Short Term Fuel Trim, bank 1
LTFT1: Long Term Fuel Trim, bank 1
While trying to diagnose a P0171, I decided to observe my fuel trims to get a feel for how they relate to what I'm…
Cognitive Hazard
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4
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LTFT way too high, O2 seems sane
Issue
Car in question is a Renault Clio B 1.2 16V with about 85KKm. I experience two issues:
Intermittent starting problems, independent of hot or cold engine. When the problem occurs I need to press the accelerator to get it to fire while…
Martin
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4
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Are (STFT + LTFT) values less than +/- 38% really normal for 2002 Toyota RAV4?
According to a 2002 Toyota RAV4 Repair Manual, "If total of short-term fuel trim value and long-term fuel trim value is within plus or minus 38 percent, the system is functioning normally."
Based on fuel trim posts that I've read or watched, this…
InfinitelyManic
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4
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LTFT high and never changes
Santa Fe 2001 2.7 GLS. LTFT is always +18 on both banks, never changes at any RPM.
STFT +4 to +6 Bank 1 and +3 to +5 banks 2 at idle.
At higher rpms STFT hangs around Zero but goes up when engine returns to idle.
LTFT never moves from +18.
Alfonso
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4
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1 answer
What is the the base fuel calculation in a fuel injected vehicle based on?
For a few years, I've been using a Bluetooth <-> OBDII adapter with the Android Torque app. One of the cool things about this is that it's taught me things about a car's operation that I may not have learned about had it not been for that data. One…
StephenH
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3
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P0101, Negative LTFT, Low MAF at idle after Short Ram Intake install 2016 Mazda 6
Installed a Short Ram Intake setup in a 2016 Mazda 6 2.5L, basically a replacement of the stock air intake system and I am now getting a P0101, weird performance stuff, and weird fuel trims.
Fuel Trims:
LTFT -8%/-10% at idle, -14%/-18% under…
James H
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3
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P0172 - System too rich
I have a P0172 on my 2011 L4 Camry. Summary of what I did:
I saw the light on, and once I saw the code, I checked the air filter. It was filthy disgusting and completely disintegrated (rat/rodent infestation). The whole filer box was full of fuzz…
Hasan Zakeri
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3
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Jaguar v6 petrol 3.0 2010 STFT and timing all over the place
2010 XF petrol 3.0 P171 and P174 and timing issue
For the last few months I’ve had both codes, so the time has come to resolve it, so far no joy, what have I done so far, the car also has a poor idle and has got worse from year one. No other error…
Pop59
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3
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2 answers
Help on diagnosing positive Long term fuel trim
My vehicle (Ford Fiesta 2014 Petrol) always have a positive long term fuel trim, which means its running lean mostly.
The log data that I recorded using torque pro can be downloaded here :
Torque Pro Log
LTFT always quite unstable, and swing from…
hudarsono
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