When I lost idle control the problem was the throttle valve switch. It wasn't sending the idle position signal. The TVS has a pigtail that connects to the engine harness at the top-front of the inlet manifold with three poles - idle, WOT and ground, so it's easy to test just by unplugging this connector and testing at the pigtail.

I was able to restore TVS function with a good external cleaning, which is fortunate, because it looks like you have to remove the metering unit to change the TVS. The two screws just aren't accessible on the car.

Duke