this is for my buddys truck (86 f250)

how can we the truck to stop going into high idle when its put in park it dosent happen everytime but most the time

 

Is the the fast idle solenoid activating when the truck is put into park or does the idle just go up when put into park? How high are the rpm's when it happens?

I'd check the throttle cable to make sure there isn't something hanging it up. The shift linkage shouldn't be anywhere close to the cable but it may be something else.

I can't think of anything offhand that would activate the fast idle solenoid by moving the shift lever to park unless it's getting power from the neutral safety switch somehow or some other wire close to the linkage shorting to the fast idle.

 

im not sure if the fast idle is activating but once it gos into park it hits about 1100-1200 i think