My 2002 F150 , 4.6 automatic is idling high. I have replaced the IAC valve,throttle position sensor,checked for vacuum leaks and checked throttle linkage with no problem found. I changed the EGR valve to clear a code. When I start the truck the rpm goes to 2000 and stays there. When I go in gear it comes down to 1200 and when i go back to park it goes back up to 2000rpm. I disconnected the electrical connector fromthe IAC valve and the idle went to 550 and I drove it home that way. It ran fine. Just a note ( that is the 2nd IAC valve Ive tried. I'm open to any advice you could give.

THANKS Tom

 

The case is clear cut for the high idle.
The IAC could be being held open electrically, allowing the high idle.
Don't change the IAC again because it's not the prime cause, as you discribed it.
The TPS has a projection that has to fit into a matching slot in the throttle shaft.
Is it in place?
If not it may be holding the throttle plate open some amount causing high idle for the same reason, to much air and possible fuel signal out of limits.
There is a balance between the IAC and the throttle plate opening at rest.
If this is upset for any reason, the PCM can't control the idle for cold starts, hot starts and normal running.
Good luck..

 

If you have a scanner, you can look at your Throttle % open and see what its showing at idle...it should be between 15% up to 21%(this is what Ive seen as normal anyhow). Check also for any kind of major fluctuation when you gently push the accelerator pedal. Something else to check just in case is your MAF sensor readings. I have seen faulty MAF sensors cause a high or erratic idle in some cases. Just a few things to look at bro, hope this helps.