87 f150 throttles high

87 f150 5.0-Engine idles and throttles high- will go 40 mph without foot on gas pedal. Changed IAC valve-no luck. Anybody ever had this problem?

is it fuel injected? if so you have an idle position module on your intake that can get gummed up and cause your prob. Ususlly just taking it apart and cleaning it will help.

Lot's of problems with starting, idling, accelerating, etc can occur at the throttle bodies themselves. I have an 89 so mine is an EFI throttle body design, if yours is the same then pop the two intake hoses off and spray throttle body cleaner into the throttle bodies themselves while someone pumps the gas to open them. Tons of black tar builds up in there interfering with sensors and the idle\accleration. If it's carbed buy some carb cleaner and do the same thing.