I am not sure if it is any different than my 87 DeVille 4100. But for my car what you do is get a voltmeter and with ignition turned on back probe the TPS sensor, put the red lead from VM to the signal wire on TPS sensor (should be the blue wire) put black lead from VM to a good ground. Typically you should have less than 0.5 Volts while the throttle is in idle position. If you have more voltage loosen the bolts and rotate the TPS until you achieve desired voltage. This assumes you have two bolts holding TPS to the throttle body and it is not pop rivetted to the TBI. Hope this helps.
The 85 HT4100 has a green electrical connector coming from the wire harness on top of the engine near the alternator with nothing plugged into it. This is the test port for the TPS and has two pins. Simply insert the positive probe into the blue wire side and the ground into the other.
Messing with the TPS can have an undesirable effect on the ISC adjustments requiring attention. Can be confusing and frustrating.
Check out some of the post covering “ISC and TPS adjustments, and get a manual.