96 Lumina Idle Problem

[jthanson]

Last month my wife was driving her 96 Lumina (3.1L motor) and the power steering pulley came off. She got it home and I replaced the pump (since it was leaking) and put a new pulley on it along with a new serpentine belt. After the replacement I tested the car and it was running rough and set a couple of trouble codes: 0122 and 1406. The 122 is a Throttle Position Sensor low voltage code and the 1406 is an EGR pintle position code. I replaced both the TPS and the EGR valve as well as the Coolant Temperature Sensor. I cleaned the MAF sensor. I sprayed intake cleaner in the intake at the throttle body. I checked the control voltage at the TPS and the EGR and they were both a perfect 5.0V DC.

None of that has changed the symptoms. The engine still revs up to 2400RPM at idle. Occasionally it will slow down to around 1600 which is still really fast for idle. My scanner gives TPS % values and it shows a smooth change across the range of travel of the pedal. I've cleared the codes and they reset every time I run the car. Any ideas what's causing this problem?