My situation: I bought a new Throttle Position Sensor and installed it. Even after clearing the ECU codes, I'm still getting a 23 (TPS), and only that code, no others. When I accelerate decently hard, the check engine light goes away... Then when I start braking, it instantly comes back on. I bought a voltometer and I am getting a little over 1 with closed throttle, and it's supposed to be around .46-.53 and at wide open throttle I'm getting around 6 when supposed to be at 5. Any ideas? I am sure this is the reason my idle is so low (500-600 at a stop, when motor is warm).

 

did you adjust it any or just install it. the '85-'89 had adjustable throttle position sensors. if yours doesn't have slots for adjustment, then you have the wrong one.

500-600 rpm idle when warm is fairly normal

 

It adjusts in a sense that if you loosen the two screws holding it, you can movie it up, down, forward, or backwards...

 

that is how you adjust it. you need jumper wires and the volt meter hooked up to adjust it.

https://www.thirdgen.org/tpimod2

this is a link to a tech article on this sight explaining how to adjust tps and iac.