When I was fishing about for information I came across this
From here =>
Idle Air Control Valve - Airflow versus Control Voltage - MBWorld.org Forums
The guy who did the measurements reckons
Quote:
...that with no control voltage (e.g., the IAC is electrically disconnected), the engine will receive some idle air - enough in some cases to cause a high idle
|
This is what I have experienced (and apparently others too) - but I don't quite go along with the reasoning just yet. May be I don't understand the system - but with a choke on a carb you get a high idle by reducing or restricting the air flow don't you? So I have been assuming that the air idle control valve is open during normal running / when the engine is not at idle but the hole closes and restricts the extra air to help control the idle...
...I think I need to go back to the FSM and see if there's any more information to be gleaned...