Thread: LTFT issue, '00 L67

Sup,

So I've got two GP's, one whom I'm swapping out an XP cam in, that's my daily. But that's unrelated.

The issue I'm having is one I've been having since a year now, it's on my '00 GT with an l67 swapped in.
So now on to explain, it's about LTFT.

Idling ; Between -7.0% and 0.0%, same in Park/Drive/Neutral.
WOT ; usually close to 0.0%, never in the +, more often in the - when it does.
Accelerating ; Usually between 3.0% and -10%
Coasting down without touching the pedal ; -7.0%

Those are all acceptable, I think, but the issue is when I am on cruise control, or keeping my speed, let say highway driving it'll stay in a okay range, then suddenly will creep up to +16.4%, and will stay pegged there till I hit a hill, coast down or give it gas, where it will go back down and stay there till it repeats this.

Now on what I've done so far is drench the engine in carb cleaner a few times, trying to find a vacuum leak, but never found anything. Now on to a gauge, vacuum coasting down is about 24.3in/hg, and idling warm, around 20 and steady.

I'm a bit puzzled. And I'm wondering, if I don't pay attention for like, a few minutes with it pegged at 16.4%, will it harm the engine? (Fact is I want to sell this car ASAP after I'm done with my XP cam build on my daily.)

Thanks for the input.

If you arent getting a lean code I wouldnt even worry about.

The only harm it can do is trip the SES for a p0171 for a lean code, it can't harm the motor, as its fixing the lean condition by adding fuel.

But another idea is to watch STFT as you spray carb cleaner, the STFT will switch way way faster than the LTFT can help pinpoint vac leaks if there even is one.

Yeah I tried that, monitored STFT, but other than varying 0 to 1.3 as they always does, nothing even flickered, even monitored rpm, and it never moved out of its normal range. It's been leaving me puzzled for a while.

But is there a possible harm from cruising without load other than keeping speed with 16.4% LTFT and 19.5 - 20.3% STFT. Because I know for sure that as soon as any load comes, LTFT goes back straight to near 0.0 but in the negative. Just been annoying me to see this get to 16.4%, but I admit that I never left it stay at 16.4 without giving a shot of gas, so I never had the code trip.