Fast Idle problem...Help, no hair...

[jsinton]

Hi all, I have one of those problems which is making my hair fall out, any help appreciated. I'm sure it's my fault, but I'm looking for a second opinion.

I have a 2003 with the 3.4 motor with 80,000 miles which had the leaking dexcool problem. It failed emissions and sucked coolant, so a fix was a must. I tore down the motor, replaced the head gaskets, replaced the intake gaskets, etc. Finally I got it back together.

I started the motor. It runs good, but now the idle speed it high at 2500 rpm. I checked the connections, sprayed water all over it to try to find an intake leak, but nothing seems to slow it down. Using a tube in the ear, I was not able to find any unusual sucking sounds. It seems hot under the hood, but the temp sensor runs in the normal range. ODB II says I have incorrect idle speed, and to look for intake leaks, IAC leaks or failure, or throttle body problems. I ruled out the IAC and the throttle body.

Do you think I messed up the intake gaskets? Some people here in this forum have said if you have an intake leak it will actually run slow or not at all because it gets so lean it won't fire. Sounds counter-intuitive to me. I assume I have an intake leak, but need a second opinion before I tear down the motor again.

Thanks in advance.

[jsinton]

Ok, nevermind, I fixed it. The IAC WAS bad! The IAC is the electrical valve mounted to the throttle body which will allow extra air to pass into the intake when the engine is cold. It's the fuel injected version of a choke. I removed it and plugged all the holes, and VOILA!... Normal idle. I replaced it with one from Advanced Auto for $47.

[richtazz]

For anyone else reading this, a vacuum leak will normally cause an increase in idle speed, not a decrease.

Jsinton, Thanks for the feedback on what the problem was, as it's helps others reading this thread.