what symptoms would be the result of a bad throttle position sensor?

if you have an auto trans, the trans shifting would be erratic as the 4l30e gets some of its instruction from the TPS.

other than that: difficulty idling, difficulty coming off idle (as in, idles fine and then stalls as soon as you press the gas..) , solid-on CEL with ECU giving code of "o2 sensor rich condition", engine and trans having a difficult time maintaining a certain common speed.. for example the engine would run fine and accelerate fine but holding 65mph might cause sputtering and erratic shifting back and forth. overall sluggishness of engine. sometimes an engine with a bad TPS will run hotter than normal at sustained high speeds due to lean condition, even if the cooling system is otherwise perfect.

It's sometimes a tough one to diagnose. If you can get at the TPS's connecting wires, an easy test that "anyone" can do is unplug the TPS (with engine off) and connect an ohm meter (multimeter with impedance gauge) from the ground to each of the other poles on it one at a time.. and then smoothly, slowly move the throttle by hand while watching the meter. this is easiest to watch with an old needle-type meter than a digital one because what you are looking for is smoothness, not a specific number. if the impedance drops to zero or shoots for the sky erratically during a sweep you can suspect a bad TPS.

is this on a V6 or a 4cyl? what year and model vehicle?

My rig is a 1990 trooper with a 2.6 l 4-cylinder engine in front of a 5 speed tranny. It cranks easily but runs extremely rich and will not idle w/o throttle being applied.After it warms up , it will stay running but will not hold a steady idle, varying by 200 to 300 rpm's. When I stop at an intersection,the rpm's will drop to about 600 and then come back to about 900, which is about where it hovers.Also, the engine feels sluggish, as if the timing were retarded but I hear valve clatter like with pre-ignition. HELP!

Try this thread for more on the tps. Have you adjusted the valves?

http://www.4x4wire.com/forums/favli...amp;amp;partnumber=1&postmarker=