HELP: Bad idle speed fluctuations.....car almost dies...???

[TeeJay3800]

May battery died, and I put a new one in the other day. Ever since then my idle speed has been fluctuating badly. It idles fine in and out of gear when at a rest. The problem occurs when the car is moving at a crawl. For example, when coming to a stop at a stop light, the engine speed surges significantly. It sounds like it may die at the low end, and at the high end of the fluctuation, its enough where I have to step on the brake harder to keep from rear ending the person ahead of me. Once in a while it will actually die when backing up after the car has just been started.

I have already done the idle relearn procedure described on 60v6.com, but it made no difference. What happened to my car when I changed the battery? Any input is appreciated!!

[geoffinbc]

Its the idle relearn.

Did you do it with a programmer? If not it makes it un certian wether or not it has been done correctly.

[TeeJay3800]

I followed the relearn procedure described on this site.

The thing is though, it generally idles fine out of gear, and most of the time when its in gear. The problem occurs while coming to a stop. Around 1-8MPH is when the revs fluctuate badly.

Could this be a IAC problem?

[geoffinbc]

Yes it could be the IAC but why justa after changing the battery.

That relearn is not correct.

1. Set parking brake, start engine in P or N position. Warm-up vehicle to normal operating temperature.
2. Allow vehicle to idle for one minute in N, Select D and allow to idle for one more minute.
3. Accelerate at normal throttle position, 20-50% untile vehicle shifts into top gear.
4. Cruise at light to medium throttle
5. Decelerate to a stop, allowing the vehicle to downshift, and use brakes normally.

Try that

[Rhedalert]

just out of curiosity, you did pull the ECM fuse that's underhood, next to the fuel pump relay/aux positive terminal, yes?

[TeeJay3800]

Thanks for the procedure, betterthanyou.

Brian, no I did not. I didn't realize the ECM has TWO fuses, lol. I'll pull the one by the fuel pump relay and try it again.

[TeeJay3800]

UPDATE: I cleaned the IAC and relearned the idle, and the car STILL has the same problem.

Is it safe to say I need to replace my IAC?

[TeeJay3800]

UPDATE #2: I've realized that it only stalls when in gear. I'll come to a stop and the idle speed will be going up and down and eventually die. However, if I pop it in Neutral, it will run like normal.

Why would the idle fluctuate and eventually die in Drive only? Torque converter issue, or IAC?

[Rhedalert]

vacuum issue or idle learn issue.