Most likely IAC valve. Most of the time you can clean the carbon buildup off yourself without having to buy a new one. I think they cost around $100. You may also want to clean your MAF sensor (make sure you only use MAF sensor cleaner spray and do not physically touch the wires). Another potential problem could be your ERG valves (2 of them one is flat another is shaped like a small cylinder) though I never really had an issue with either of those before. Hopes this helps.