My girlfriend has an '03 Elantra and it'll occasionally rev up to like 2-3k for no reason. Sometimes it does it as soon as you start the car and then it'll stop after a few seconds or it might start and idle fine but then rev up. It feels like the idle air control just goes wide open. I'm going to check for vacuum leaks but it's not a continuous issue, just sometimes. Any thoughts?

 

Yes, the IAC would be my first suggestion to check.