Idles too high/

Hi, It sounds like one of two things, first, do you hear anykind of hissing when you are under the hood? Because that would mean a vacuum leak and would cause a constant high idle, two, the idle air control valve could be faulty, and actually there is a third one, the throttle position sensor may also be faulty, let me ask is there a check engine light on? If so, then I would take it to autozone where you can have it scanned for free and pinpoint which of the three is causing this.
Thanx
jody