TP sensor/idle problem?

[gizmo83]

my 87' 2.3L EFI is idling bad... revs up and drops down, revs up an drops down, ect... if i unplug the TP sensors, it idles just fine. i've check the TP sensors with a volt meter and it checks out good. even still i went and got a new one, which i think was defective because it read 5.01+ volts at WOT and at an idle. never droped below 5 volts. so i put the old one back on. and with the old one back on it idled fine for a few hours then starts idling bad again. also it usually (not always, but usually) idles fine in the morning when its cold. then after it warms up is when it seems to start idling bad. (unless i unplug the TP sensor then its fine.). could the heat be messing with the TP sensor or somethin? whats the problem here?