Originally Posted By: carwreck
On GM 3400, erratic idle can be fixed sometimes with the FM (F*** Magic) IAC reset procedure:
Reset ECM by pulling ECM fuse (under hood) for a few seconds or disconnect battery for a few seconds.
With A/C turned off, start car and immediately put it in Drive with your foot on the brake. If the car does not start initially, keep trying WITHOUT putting your foot on the accelerator.
Let the car idle in gear for at least 5 and no more than 7 minutes.
Shut off the car for 10 seconds.
Start engine, place in drive and let idle for 5 minutes.
Shut off engine.
Idle is learned.
Ok, can't find the fuse for the ECM. None of the fuses are labled "ECM". I do, however have a big friggin' sledge hammer handy just in case I need one!