Rich at Idle

[michbc3]

Understand that I haven't had very much seat time since installing ecu-GN. The car runs great off-idle - takes fuel well at moderate loads/speeds. But the A/F ratio at idle is consistently richer than target by almost 2 A/F. Fuel pressure gauge reads normal. When I tried adjusting VE to lean it out, the idle quality goes bad. I adjusted the TB to get the IAC at 19 or 20, then re-adjusted TPS. No good. I then suspected potentially leaky fuel injectors. So I pulled them out and had them tested and cleaned. All ok. I need to develop a new plan of action. Perhaps I should try to do "auto-tuning" at idle?

This is an 89 Trans Am Pace Car. 72 lb Accel Injectors. Roller cam is 206/210 and 0.506 lift. KB throttle body.

 

[EricM]

The first thing to do is get the target AFR and actual AFR to match up (within reason).

Its richer than target because VE is too high at idle, and the fuel correction is at the lower limit. You need to lower VE until the correction is around 100, so the target AFR and actual AFR are close.

Then, if the engine doesn't like that and the idle is unstable, richen the AFR target (not VE) until it smooths out.

Every engine is different and sometimes you'll need to command richer than you think. The 12.5-13.5 AFR range is pretty common.

Let us know how it goes!