What would cause the throttle on a 1988 F-350 to stick when the motor and outside temp gets hot? i have sprayed all of the linkage etc. and installed a heavy return spring. For some reason after the engine gets warm it seem to idle high.

 

A bad throttle cable would do that. My neighbor had an F-350 with a 351 that did that. Soaked every linkage as much as he could, but the cable itself was still getting caught up.

 

I assume that it's injected... if it's a sticking throttle in the throttle body - Engine OFF - Remove the air intake tube to the throttle body and clean the inside of the throttle body where the throttle butterfly touches (or almost touches). Do this by spraying Carb Cleaner onto a rag, holding the throttle wide open (i did mention engine off...) and then wiping around the inside of the TB. Don't spray the Carb Clean directly into the TB as it can swell orings and seals. Make sure that there is no debris on the edge of the throttle butterfly as well. Put her back together and let her idle with no load (A/Con or electrical) for a few minutes to relearn the idle setting and you should be good to go. if it ain't it's the cable as per Lead Head...

Good Luck
Kiwi

 

Thanks, I went ahead and changed it with a used one. Now I have to get my foot adjusted j/k.

 

A used cable or throttle body?