try cleaning the IAC and the throttle bore. They say 'DO NOT CLEAN' but clean it anyway. make sure you disconnect the battery afterwards for about 10-15 min before you start the car, then let it idle in drive/auto trans nuetral/manual trans for 5-10 min with all loads off (a/c headlights etc). It is also possible the IAC just quit working, and needs to be replaced. There are many other possibilites but those are the most likely causes.
