Toyota Repair: 1997 T100 High Idle, mileage engine, engine temp

Question
I purchased a 1997 T-100 from someone living in Boulder, Colorado. Now  back in Wisconsin, the truck always idles high... 2000-3000 rpms.

IF I rev the engine at idle (up to 4500 rpms), the idle sometimes drops to 1400 rpm, but then jumps back up to 2000-3000 rpms once I shift into and then out of gear. Is this a tuning issue due to differences in altitude? What could be causing the problem?

The throttle body has been checked and lubricated. I took the truck to the dealer and they couldn't figure out what was wrong after a $95 scanning job.

Answer
Mileage? Engine?
Auto/Manual?

You should get your $95 back. The charge was for a diagnosis, none was given.

The engine temp sensor would be suspect as thats the main thing the ecu uses to determine idle speed.Replace it.

The Idle air control motor mau be worth checking also, but they usually stick closed , not open, and the symptom would be opposite.(Idle too low)


Mike