88 90 Quattro fluctuating idle

[Huw Powell]

> Mine does that too. I Unplugged the ISV, the oscilations  became with
> less RPM peaks.

> So the problem was not the ISV (i cleaned it anyway), somewhere in
> the loop change to fast causing unstability.

I suspect teh idle switch.  If it's not closing, the ECU does not know 
to regulate the idle with the ISV.

> I unplugged the mudulated valve to the distributor and it stop. BUT
> at cold  starting i got problem: cant start, i plugged that module
> again , then start again..

Yeah, well, that would happen.  That "valve" is how the ECU enriches the 
engine for cold starts...

>> Sounds like a gummed up ISV. If if only happens when warm, that
>> means the engine should be in a closed loop with the ECU & ISV
>> controlling idle. ... That said, it could also be a vacuum
>> leak...

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/