I have a 92 F-150 with a 302 in it. My problem is that from time to time my idle runs up to 3000 between shifts. It will idle down after a couple of seconds but will continue to do it between all shifts. It dose not do it when I start up, only when I step on the gas pedal. Most times if I turn the engine off and crank it back up it will correct it self but this happens nearly every time I get in my truck.
I never get a check engine light and I hate to take it and have it put on a computer just to find out it was something simple. Any help would be greatly appreciated. Thanks...

 

Have your mechanic check out the Differential Pressure Feedback Sensor (part of the Exhaust Gas Recirculation system). It's located just to the right of the throttle body (2 small hoses and an electrical connector go to it...both hoses run to the metal piping that runs from the exhaust manifold to the inlet of the EGR valve.)

Edited: Oops!...I didn't realize the age of your vehicle and don't know if you have a DPFS. I posted a possible target area for a later model 4.6 or 5.4.

Sorry!

 

I have this very same problem with my 94' 302 150 and have been unable to fix the problem all the way. I have reset the computer by disconnecting the battery, then restarted the truck and let it idle for five minutes or so before driving it. It did seem to help some but still has the high idle between shifts when I shift at 1.5k rpm or higher.
Do you happen to have the a non-stock exhaust system?

 

Yeah, I changed it out past the cat. I split it into duals and left the mufflers off. But I ran it that way for several years before the problem ever started. It did start not long after I replaced my rearend though. At that time I replaced the air/fuel mixing component. Sorry the name of it excapes me at the time. That helped to some extent. Before I did that it was every time I drove and it normally would not idle down at all.

 

I've had the same problem, ended up (both times) being a simple vacuum leak in not so easy places to find. Took it to the dealer the first time, they were totally lost. They had a new computer installed, new MAF, new 02 sensor, etc... Eventually found the vacuum leak myself and made the Ford dealer (Sunrise in Los Angeles) pony up a refund. They were good about it but, it was disturbing that THEY couldn't find a basic problem like a vaccume leak.