Then you're going to need a scanner that displays live data to see what the computer is doing. The automatic idle speed motor will be shown with the "step" it is on from 0 to 256. 32 is typical for a properly-running engine. If you find it on a lower step, and the idle speed is too low, it hasn't relearned minimum throttle. One defective section in the brake light switch can prevent the relearn from taking place. If you find it's on a higher step, say 45 or more, the computer is trying to raise idle speed without success. An open circuit in any of the four wires going to it will be detected and set a diagnostic fault code. That will most likely not turn on the Check Engine light because it shouldn't have an adverse effect on emissions. The motor can not be tested accurately with an ohm meter because there are four coils of wire inside it all tied together. Two of them would have to be open to see that with an ohm meter, and it is very uncommon to even have one coil open.
Besides electrical problems, the air passage could be plugged with carbon or the shaft of the motor could be tight. Carbon was a big problem with the 3.0L engines in the early '90s, but we don't see that anymore with better additives in the fuel.
Two ways to see if the motor is tight are to remove it and see if the valve moves in and out when you turn on the ignition switch, or to use the scanner to perform the AIS control test. By pressing buttons on the scanner, the computer will run the engine speed up to 2000 rpm in 200 rpm increments.
You can also retract the pintle valve by hand when you have the motor out but it will be very hard to move. You'll have to use both hands to squeeze the valve in or pull it out. Once it has been retracted, you can install it that way and start the engine. Idle speed should be much too high but it will come down gradually as the computer pulses it to the desired position.
You can also try holding the brake pedal up with your toes when coasting to do the relearn. If that works, the switch could just be out-of-adjustment and road vibration is making one part of it turn on and off.
Thursday, January 19th, 2012 AT 7:06 PM