High idle and sometimes sticks around 3000
 

I replaced the TPS on my '91 F-150 5.0L about three months ago. Since then I have been having a problem with my idle hanging around 1500 all the time. Every once in a while it will idle just under 1000 where it belongs. When it's cold it likes to stick up around 2500 - 3000 when I let up to shift. Usually when I tap the accelerator real quick it will idle back down to around 1500. When I replaced the TPS I pulled the entire throttle body off and cleaned it completely, so my butterflies are not sticking and it does not feel like my accelerator cable is sticking. I pulled off the front half of the IAC and cleaned it out really well too. I also scraped all of the silicone sealant off the throttle body and replaced it with a gasket. When I idle it up under the hood the spring is returning the trottle to original position but the idle still sticks around 3000. Is there anything I missed besides buying a new IAC?

TPS might have been installed incorrectly, which would give you a high idle. For example, if you were to remove the old TPS you would first want to scribe a match mark for an easy reinstall of the unit. You would install on the throttle shaft then rotate (clockwise only) to match up to your marks. Have a look here for some tips for adjustment of your new one.

Ford Fuel Injection » Throttle Position Sensor (TPS)

Thanks for the help Slip Ford Man I will get to work on it later this week

Just a word of warning. What ever you do, do not mess with the set screw on the throttle body to adjust the idle. That's not what it's for.

Yeah, I caught that from another post I read through. I heard it's factory set and once moved there is no fixing it.