I've had the same problem. Its the IAC as stated above. In my case, it did the exact same thing right before it completely crapped out and would then just idle at 1800 rpm. I think the heat, or something causes them to lock up in the open position. Try spraying it out with carb cleaner. If that doesn't work, head down to the junk yard and grab a couple of the damn things, usually like 10 bucks around here. I found two of them at the local yard that were brand new. Beats paying 80 bucks for a new one, only to smoke it too.