Ive been reading a lot of forums about testing the Throttle Position Sensor, and everyone says that once installed the sensor should measure anywhere from .9-1.0volts when throttle closed and its even better around .95v. Haynes manual says anywhere from .5-1.0v. Well my sensor was only read around .78v closed so i adjusted the sensor so that it would read .95v closed and when i ran my truck, the rpms was insanely high at idle . Does this point to an issue like a warped throttle body or should i just leave it alone? i dont have a tps engine code or anything but i do have code 13 which is rpms in the high range at idle and some hesitations when driving(before messing with tps). The ohm reading for it are within range. I could tell that the sensor has been replaced before but i have no idea what brand. Anyone have any experience with this?

 

I would retest it, both voltage swing and ohms while disconnected. Both should be smooth and the voltage goal is 1.0V. Make sure your mechanical fit is allowing things to move through the entire arc. Make sure your battery voltage is 12.8 vDC or better, if the battery is weak, the TPS may not be smooth or correctly doing it's thing.

I would test the IAC (or what ever they call it for your 1990) to make sure it is working as well as it should.

I would make sure to buy a ford/motorcraft, if you decide to go that route.

rpm will go to 900-1300 upon cold start/high idle, not sure if that is "insane", then drop down to your normal 650-750 or so.

Make sure no one has munged up the throttle plates, trying to "fix" something and that they move freely and close cleanly and completely.

 

So it was WITHIN spec.A) WHY???
B) The sensor is not adjustable. What exactly did you do?Sounds like you tampered with the throttle stop screw.