fuel trim a problem?

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Dakota1820

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Apr 28, 2011
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3,894
Location
missouri usa
abslt tps 0.0
eng speed 849
calc load 2.04
map "hg" 8.6
coolant 203f
iat 93f
ign adv 15.0
st ftrm1 0.8
lt ftrm1 -19.5
veh speed 0
fuel system 1 clsd
fuel sys 2 n/a
02s11(v) 0.275
st ftrm11 1.6
02s12(v) 0.330
obd2 stat ca

this is the readings from my actron scan tool for my 98 saturn sl2 it had been idling about 15 minutes at the time these numbers were recorded. the -19.5 looks out of wack. ive been getting 34.8 mpg so i am confused. anyone care to throw some input at it?
 
Because it's reading negative the long term fuel trim reading is representing a fuel cutback likely due to the extensive idle. The short term number is perfect.

When you see high positive readings for long periods of time it might represent a unmetered air leak in the induction system. I personally don't see anything wrong with these readings after a 15 minute idle time.
 
While driving it was at about -7 but going down a steep hill in second it went all the way to -21 the stft was normally around 0 or a hair negative
 
While driving it was at about -7 but going down a steep hill in second it went all the way to -21 the stft was normally around 0 or a hair negative
 
I made a thread a few weeks ago asking about long term fuel trim on deceleration. It seems that during deceleration it's fairly pointless to look at fuel trims.

Most sources I've seen say that if your LTFT is under +/- 10% under normal driving circumstances you're in good shape. I wouldn't be concerned about the large negative LTFT after 15 minutes of idling, there's no telling what was going on in the enging after sitting for that long.
 
i talk to my instructor. he said my numbers were a hair high but not high enough to worry. he asked if i had just driven it a long way on the highway i said yes and he said that was another reason it would be high. the number while cruising were 7.0-7.5 and the stft was fluctuation but generally between /.3+ to .3-
 
Yes, decel always seems to have high negative fuel trim numbers. I think it may be due to decel fuel cutout. I will have to remember to check on my car while its cold before it starts enabling that feature.
 
Originally Posted By: Colt45ws
Yes, decel always seems to have high negative fuel trim numbers. I think it may be due to decel fuel cutout. I will have to remember to check on my car while its cold before it starts enabling that feature.

Yeah, Im 99% sure its Decel fuel cutout. I remembered to switch the SGII to LFT1 prior to me letting off the gas at 50 with O/D off and CHT at 115F. The most I seen was -5.
 
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