The car has been idling high at startup for over a year, as high as 2800 rpm. The rpm will increase with electrical load, (turning on the A/C, headlights, etc) and (usually) drop when removing the electrical loads. The car will idle high when coming to a stop light and will usually drop to normal when coming to a complete stop though sometimes I'll have to turn off the A/C to get it to drop. Looking at the Idle Air Controller with Torque Pro, it can read as high as 122 counts out of 255, which let's me drive in 4th gear at 50mph without touching the gas pedal sometimes. Normal idle, around 800 rpm with the A/C on, is around 50-70 counts. The IAC is doing what the PCM is telling it to do. But why?
The car is at the shop and the (competent) mechanic, and myself, are stumped.
IAC, PCM, ICM, EGR valve, LIM and UIM, Valve cover gaskets, and Throttle Body have been replaced with new or from known good, running engines. No vacuum leaks have been found. The PCM is NOT throwing a DTC P0507 Idle Control System HIGH RPM code.
Please help.
