1990 F150 5.0L V8 Throttle Position Sensor?
 

So, I recently ran codes on my truck, and the TPS was below or above voltage, I believe it was below, but I forgot to write it down at O'Reileys. I bought a new sensor and was hoping someone could give me a brief but informative guide to replacing it. I know it's on the bottom of the Throttle Body where the two hoses from the air intake meet, and it's next to the air inlet sensor. I likely have to take of that piece, the one the air hoses attach to, to get to the sensor on the bottom, and I should get a new gasket to put on it when I reassemble. What is that gasket called? Anyone have any good information for this? Thanks.

Also, I'm curious as to what a bad TPS would affect in the performance on the truck, currently, when on the highway cruising anywhere above 45-50 mph, where it's in overdrive, if you let off it goes into extreme engine braking and slows down quickly, also if the throttle is barely applied it goes back and forth between closed throttle and barely open. Any ideas?

Thanks Guys

Yes a bad TPS could produce the symptoms you describe and it will also affect transmission operation if you have the E4OD. To change the TPS the whole throttlebody has to come off.. that is the part containing the throttle blades.

Great write-up here: Ultimate Throttle Position Sensor (TPS) Thread - FSB Forums

I do have the E4OD, what would it do to effect it? Shift timing?

That article was amazing RLA, thanks for showing that to me. Sounds like a got a project for Saturday night now after I buy some snow tires too.

The PCM uses the throttle position in the calculation of when and how hard/soft to shift.

Sooooo.... it'd be what's likely causing my sometimes hard shifts then, that I didn't mention earlier because I supposed it irrelevent...:-hair

So, UPDATE:
I changed out the TPS, and it was AMAZING results.
The transmission now shifts seamlessly, I'm not sure on shift timing because I don't have a Tach yet, but it seems correct.
The idle is alot more stable now, previously, it'd die in the morning when I started it up, unless I held down the throttle while it warmed up.
The throttle is ALOT more responsive and has alot more get up, torque is alot higher at a lower throttle position now.
The engine doesn't die out when you let off the throttle on the highway, previously it'd drop out of overdrive if gas wasn't applied at highway speeds.

I'd like to thank the guys that helped me with information for this, this really is my dream truck, it's a project, but It's coming together nice, I'll post pictures as I can get some on the computer.

Now I just need to change out the U-Joints and likely the fuel pressure regulator, then the exhaust, then basically just some cosmetic things.