So let me see if I understand how the idle system works- the idle speed motor is electronically controlled by the idle speed ECU. The idle speed motor controls the throttle plates by vacuum. So I've deduced that my idle speed ECU is the problem after all of this. Am I correct?Not quite.The idlespeed motor is an air valve and allows a dynamically controlled air flow to bypass the throttle plates. However, I think you're on the money and it's the idlespeed ECU. Can you try another one? It may be the idlespeed thermistor too, but that's a pig to get to