faulty throttle position sensor?

I took my wifes 93 lumina euro to the grocery store today. While i was driving i noticed that the Service light was on. When I stopped at the first traffic signal, i noticed that the Tach was bumping between 500 & 1000 RPM. Upon acceleration the throttle seemed to spike as i barely pressed it.

2 part question:

1) Would this be an indication of a bad tps?

2) If so where exactly where would i find it.


Thanks in advance.

Yes, it sounds like the TPS, and it's located on the opposite side of the throttle plate from where the cables attach. The tps sits directly on the throttle plate's pivot shaft....

Notice any weird shifting too?

It could also be the idle air control valve (IAC). Maybe?

Thanks for your help.
Today i replaced the TPS. however , in the process i had to remove the thing that sits on top of the throttle body. im not sure what it is but there was a gasket on it that was old and broke when i removed it. what the heck is that thing called?

by the way, it took me about an hour and every curse word that i know to replace the TPS! it wasnt difficult, there was barely enough room to get the TPS of and back on again.

I believe the other piece is the IAC valve. Does it mount with two screws and have a cone shaped pintle that goes down into the throttle body? If so, then it is the IAC valve.

I believe the other piece is the IAC valve. Does it mount with two screws and have a cone shaped pintle that goes down into the throttle body? If so, then it is the IAC valve.

very close the piece that i am refering to is a plate that bolts to the top of the throttle body and the IAC bolts on to it. there was a gasket inbetween the throttle body and the plate that bolted to the top.