Why am I getting LTFT's when in wide open throttle. It never use to do that. They (LTFT's and STFT's) use to always go to '0' in wot (fuel trim cell 15). And. does the MAF(lbs/min) and the MAF (hz) look normal? Should they be smoother? Not like a saw blade like these some times do.
long term fuel trims always can be carried into WOT during transition - I always disable LTFT's in my tuning to prevent this issue
fuel>oxygen sensors>ltft enabled - set to disabled and set minimum ECT to 280*F
Positive LTFT's will carrying into PE. Negative LTFTs will not.. Been that way with GM since the 80's.
Tuner at PCMofnc.com
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Alvin, that's good info. So in short, your LTFT carryover can make you richer than desired, but not leaner?
Yes.. It can show a negative fuel trim in PE but its not actually taking fuel away.
Tuner at PCMofnc.com
Email tuning!!!, Mail order, Dyno tuning, Performance Parts, Electric Fan Kits, 4l80e swap harnesses, 6l80 -> 4l80e conversion harnesses, Installs
So why would it start to do this recently? Fuel trims have always gone to '0' at WOT before. And did anyone look at MAF graphs in the log? They look choppy like there might be a wiring problem or a sensor problem?
I leave this GM feature. I never disable the long terms unless it is temporary for tuning. This feature exists to help prevent the engine from leaning out if there is a vacuum leak (unmetered airflow) or low fuel pressure. If its lean when it goes into PE it adds the same amount of fuel as the value of the fuel trim value. +5% LTFT = +5% added fuel. The fix is to dial the VE/MAF tables in slightly rich and let the PCM pull a little fuel as it learns.
+1 ^ voteOriginally Posted by Fast4.7
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