What causes the idle speed to fluctuate?
What causes the idle speed to fluctuate? A leak will cause fluctuating idle speed. If no vacuum leak is found, then my next suspect would be the Idle Air Control (IAC). Are you saying that this started happening after you replaced the throttle body gasket? What happens when you idle the air control valve? Normally, if you just start your car, the idle air control valve will cause the engine rpms to increase and slowly decrease. That would be a sign that your IAC is working. What happens if the idle level is too low? Idle level too low. If...