where is the throttle position sensor on a 1997 chevy lumina?

The TPS potentiometer internal shaft has to rotate with the throttle shaft, so locate the throttle shaft (hooked to the accelerator cable) and look up the TPS for your make year model on http://www.autozone.com/ click on replacement etc.

Is the check engine light on? A bad TPS is kinda rare. Does the engine RPM go up n down with the gas pedal? If it runs rough or conks out at red lights, it could be the IAC (idle air control). Or it could have an air leak on the throttle body, spray some starting fluid around it while the engine is running, the RPM should not change. Go to a parts store, Chilton's put out a manual on engine emission systems, it tells you how to test each part, I have that book and it has paid for itself! I bought it while I owned a Chevy Beretta, under the hood it's the same as a Lumina

Have someone move the gas pedal up and down. Watch under the hood, the throttle will be moving. The TPS is the electronic gadget on the other side of the throttle body. Disconnect the negative battery cable before unplugging any sensor under the hood.