johnstronaut

I have an 87 F150 with the 5.0 302. When I start it in the morning to head to work she idles just fine but as I get down the road and kick the clutch in, it'll spike real high to 2500 rpm. When I park it and put in neutral it does the same thing. But like I said, if I leave it for a few hours and start it, it won't have high idle. I was thinking maybe it was a vacuum leak plbut I'm not noticing any power loss when I'm accelerating. Thanks guys.

fltdriver

Pull your codes, test the TPS, when you are having this issue turn the truck off and unplug the IAC then restart it (if it idles normally then the IAC is the issue), clean the TB blades.

Could also be ECT sensor as it may be giving a super low (false) reading and the PCM is trying to compensate by "warming" the engine up.