My 1997 Silverado idles very high (12-1500 RPM) at all times, pretty much. Someone mentioned that this may be the TPS causing the ECM to go into a "factory default mode"? Any help? Truck is a daily driver, and I could definitely be getting at least SOME increase in fuel efficiency, if this problem were dealt with. Thanks!

 

That should have your check engine light on, have your code checked.
My 97 with a similar problem (It was sporatic) was the tps.

 

My manual says to test the voltage on the grey wire to ground (with the connector removed from the TPS) and you should have 5.0 volts (with key on). Then, reconnect the connector, and you should have 0.6 volts from the blue wire to ground with the throttle closed, and it should vary to 4.5 volts steadily as you open the throttle. I recently tried this on mine (93) and it worked as described. Manual covers 1988 to 2000 models.

 

Thanks to all who've responded with helpful information on this issue. I will replace the TPS asap,and post the results. Hope everyone is having a great day!