I have a '92 F150 ( 2WD / 5.8L / E40D ). It has 123k on the speedo. After this truck warms up the idle will drop to what seems a normal rpm but after driving it comes back up, sometimes way up. Sometimes I can get it to drop back down by goosing the throttle but that doesn't always work. I haven't pulled any codes yet so i'm not sure what will kick out. Any guess out there as to what it might be?? I'm thinking TPS. What about the temp sender on the intake manifold? Is it a common failure?
Thanx in advance for all of your input!
Mike

 

The temp sender only works the gauge on the dash.
The temp sensor is a possibility - it's on the stand up pipe just above the thermostat housing (at least it is on a 5.0 - should be similar on a 5.8)