Hi Glen..

The IAC on the back stands for "Intelligent Air Conditioning"
as I said, sort of a hybrid system..

The IAC (Idle air circuit) is part of the BAC valve (bypass air circuit)
The BAC is the cold start device, and is controlled on the older
models by water running through it, as the water heats up, the valve
closes.. in contrast, the IAC is what controls the idle speed, and is
done electrically, through the ECU.. when the ECU senses a load on the
engine, such as power steering, or electrical load from lights etc,
then it opens the IAC valve and brings the rpm's up a little..
The whole BAC/IAC valve is bolted to the throttle body, on some models
it's underneath, some are on the side, but you will notice it has an
electrical connection.
Don't confuse it with the TPS (throttle position sensor) as that is a
pig to setup.

Glad to hear you have sorted the gear problem... It's usually
something simple on these, as very little goes wrong with them..


John