1997 Chevy Lumina 6 cyl Front Wheel Drive Automatic 235,00 miles

1997 Chevy Lumina with 3.1 engine. The car idles very fast upon start up and the high idle gives the trans problems shifting until upper speeds are reached. TPS code came up and it was replaced. The car then ran ok intermittently but after a day was back to the same problem. The same TPS code is present. And am now also getting the p1406 code for egr system. The intake manifold was cleaned and egr valve replaced 5 months ago. Also the throttle cable was replaced at the same time the tps sensor was replaced. The throttle cable was badly worn. If i detach the plug from the Idle air control valve the car idles even faster. i don't know if this is supposed to happen or not. Could the IAC valve cause the car to race?

Hi:

Several things could cause the vehicle to idle fast. It seems that you are on top of them. However, have you checked for a vacuum leak? GM's 3.1L V6 engines have a reputation for intake gaskets leaking.

Let me know what you.