Anyone know how to test the idle air control valve? I have a friend that just bought a 99 trans am. His car has a random misfire on almost all cylinders. He had a weak #8 coil pack and changed it but the car still runs really rough. He thinks the idle air control valve might be the problem because he read that if you pull the connector while running there should be a change in idle. His doesn't change.

Anyone know the testing procedure?

Matt