Oscillating Idle

[Huw Powell]

> I'll have to check the idle switch tonight, but I don't think it's that 
> because it acts different when it's cold.

> I've also never heard of a bad idle switch making the idle oscillate like 
> that. Doesn't a bad switch usually make it idle rough all the time if it's not 
> working ?

Idle is a special case of closed loop operation.  The closed idle switch 
tells the computer to use the ISV to regulate the idle speed, it also 
affects the ignition advance (electronically or vacuum/mechanically, 
where applicable) to conserve fuel, etc.

If the idle switch is open, the engine can do all sorts of silly things, 
like rev too high, oscillate, etc., since the ECU isn't doing what it 
usually does to keep things nice and calm.

Easy enough to check, though.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/