2003 Explorer 4.6 RPM surge on cold startup

[titan7]

My 2003 explorer limited 4.6l V8 has 99,600 and the other morning I started it up and the RPM ran up to 1500 for 10 seconds and then dropped to 400 and then surged up and down from 500-1000. When in drive, not as noticable. When warmed up it comes and goes but it's still doing the same thing. I pulled the cover off and looked for broken hoses and listened for airleaks but can't find anything. I took the MAC off and the wires look clear. Before I take it to the dealer to get bent over, any other suggestions???

thanks!

 

[matt0248]

Could be anything from a vacuum leak at the intake gaskets, intake elbow, air intake system, pcv lines, and evap lines. to a bad IAC valve. when the engine is cold you can start it up and spray a little brake cleaner around gasket area and vacuum hoses. if the idle stabilizes when you spray in a certain arear there is your vacuum leak.