I have a 1991 F350 stake body. My problem: the truck starts just as it should, but the moment I put it in gear and touch the accelerator, the motor speeds way up ( 2000, 2500 rpm). If I shut the truck off and restart it, the idle has returned to normal. The linkages are not sticking. Any help would sure be appreciated.

 

sounds like a tps sensor. did you scan it for codes?