Idle question: cold or hot, it hunts after start


New Member
Sep 30, 2001
I have an idle question (again).

When I start my motor, cold OR hot, for a period of time after starting, the idle will not stabilize. Often times I have to tap the pedal a few times to keep it alive, and once it will run on its own, it will 'hunt' for the correct RPM. However, as soon as it enters closed loop, it settles down and idles fine.

A few times this weeekend I pulled up the Dashboard to watch what happens after cranking. The one thing I see that seems out of whack is the Actual O2 is reporting full lean (15.94). The MAP sensor is all over the place as the RPMs jump and fall. But the IAC and VE seem to start mostly static.

I just figured that I had the VE entries way too lean in the IDLE space of the VE table. However, as soon as it enters closed loop (from a cold or hot start), the O2 correction makes it look like the VE tables are too rich (I see -5 to -10% O2 correction at IDLE).

I looked at the After Start Enrichment vs. CTS table, and it shows 0.4% enrichment at hot start temps. It's about 20% at 16 degrees F, and a straight slope down until 140 degrees. I think this is exactly what was in the demo.gct file.

Before I randomly start changing these tables, I'm hoping someone can point me in the right direction. Since it idles great once it goes into closed loop, I don't understand why cold or hot it's so unstable until it enters closed loop. Is there some other table I'm missing?


PS: I'll be glad to post my GCT file if looking at my tables would help anyone! :)
Given what you have posted, I think you need more afterstart fuel. That will keep it from being so lean. However, the ECU won't go into closed loop until the afterstart fuel is completely decayed out, so it may take a bit longer for that to happen. Adding afterstart should cure the lean rolling problem though, at cold temps and at operating temp. I usually stuff 10 or 15% in at operating temp.