how did yours act before you changed it? mine is very sporadic at idle. like bounces from around 200 rpms to 900rpms for around 10 seconds then evens out
Didn't have issues when cold, but once hot the idle would just be s***. Not every time, but about half the time I would pull up to lights, the rpms would just rhythmically bounce from ~0 to 1000. It wouldn't die but it would just keep bouncing rhythmically every 2-3 secs, like that. Was very annoying @ red lights, lol. Almost made it seem like I was revving it on purpose like that, which made me feel like a jackass... lol
I would like to know the symptoms of a bad IAC as well. For whatever reason my car's idle went to s*** after changing the pass. motor mount saturday. It idles then it stumbles some but doesn't ever die, it runs fine when not idling. I only got one CEL that hasn't yet returned, P0171. Also while coasting in neutral and slowing down the engine doesn't settle to idle as quickly as before, it stays at about 1100 rpm and then drops.
This doesn't necessarily sound like the IAC, but it could be. Vac leak around the intake mani, maybe? Have you checked for cracks around the VICS actuator on the IM? I've heard of hairline cracks there.