do this. (i had the same problem)

take off the intake, so you can see into the throttle body. start the car. there's a little hole in the side of the throttle body, plug it up with your finger (it's the iac valve i believe) when you plug it up with your finger and the idle is normal, then you know that it's that valve.

next turn the car off and all. take the throttle body off. the iac valve is on the underside of the throttle body. take it off, unscrew the end of the valve. i don't quite remember what it looks like, but it's easy, inside there's a plastic thing with threads, and a springs. screw the plastic thing all the way back in, it probably just came unscrewed. put it all back together and it should all work fine. it did for me at least. g'luck.