DriveAk

I have a 88 f150, with the 5.0, and an auto trans., and just the other day when i got in my truck, the check engine light was on, checked the codes, the codes read TPS out of range. Today, I went out to my truck, started it, drove to school, and it was idling high the whole time. When i got home, I started it up, still idling high, but when i disconnected the TPS, it kicked down to a normal idle, plugged the TPS back in and it kicked up to the high idle.

AuroraZero

You have diagnosed it correctly. Just did one on mine. Fairly easy to fix really.

Bibo1985

May wanna clean your IAC too, I just ordered a new TPS for my 95. Before you buy a new TPS, try cleaning your IAC and test the TPS with a multimeter, there's a post on here somewhere with a youtube link showing how to test for a complete circuit and for operation. Chilton gives a simple test, which mine passed, but when I checked the range and reference voltage, both were double what they should be.
Good luck!

DriveAk

thanks for the info, and the IAC is relativly new (got an IAC for a 5.8 from my auto teacher) it bolted right up. it used to do the high idle before I changed the IAC. afterwards, it ran great for awhile, now it's the dang TPS.