question

[Trever]

i have a 87 Ranger 2.9 5speed and was woundering if the throdle postioning senser is affected by heat

 

[Jspafford]

Not heat normally found under the hood of an engine. Fire might melt it though, but you knew that.

 

[Psychopete]

Honestly, I think your problem is something electrical.

The fact that it acts up when it's "warm" (closed loop), and that you have 30lbs of fuel pressure sort of eliminates a lot of possibilities. When the engine first starts, it uses tables of information stored in the computer (open loop) for certain sensors (which ones specifically, I don't know), then uses the actual sensor data once in closed loop. Like the o2 sensor won't function correctly when it's under a certain temperature, it needs to heat up first.

You said you have an OBD-I scanner, but never answer whether you got the "no error" code, or if it just didn't do anything at all. Given what I said above, this is generally a good starting point for diagnosis. Although, if you don't want to diagnose, take it to a shop.

Or you can just arbitrarily replace ALL of the sensors and hope that fixes it..

Pete

Edit:
If you suspect the problem is the TPS, that is testable with an analog voltmeter. There's a ref voltage that's +5 always, sig wire that's +0-5v (at idle, the base is usually ~.9v), and a ground. It's not too hard to figure out which is which, just backprobe the TPS plug and you should be able to figure out. You'll want to test between the ground on the plug and the sig 0-5v. It should sweep smoothly to ~5 volts when the throttle is taken to WOT. If it has any dead spots, it's shot.