Is it normal for idle trims to jump around at idle with a cammed car?

[mvvette97]

Hey guys I was just doing some logging and tuning on my trans am. The cam is a 228/230 on a 112lsa. I was watching the short term and long term fuel trims and notice that during idle the short will jump around from -5 up to about +1 and the long term will stay in the -5 up to about -.08. Is this normal with a cammed car? I tried to get them both around -1 or 0 but then it tends to jump up in the positives. The car runs fine with no idle problems and the wideband says from 14.5 to 15 at idle. Do the trims tens to jump around because of the rough idle? Also just to throw this out there while driving steady the long term trims run in the -4 to -5 at light throttle but when a little more thottle is added like driving up a hill they will get in the -2 on up to 0. Am I prettygood or am I just chasing my tail trying to get a cammed engine to be perfect?

[WeathermanShawn]

What you are describing is perfectly normal. STFT's are notoriously 'jumpy', so I tend to go with LTFT's. Both your Idle and Throttle descriptions sound perfectly normal. I tend to go with an average LTFT over a 45-60 minute Log. A good goal is an average of ~ -1-3%.

So day after day you should remain at about that average. A few notes. Of course after a fill-up Trims go radically negative for about 15 miles. Probably related to Fuel Temperature (colder). Also E10 gas vs E00 will cause about a 4% difference in Trims.

So, IMO you are just about where you need to be, especially with your wideband verifying your AFR..