odd idle problem

[quk@sievers.com (Phil Payne)]

In message <199707150352.UAA16701@sesame.columbia-center.org> "Michael and Portia Loeks" writes:

> I'd second that opinion. BTW the reason it surges is because of the decel
> valve. The decel valve is invoked if the ECU sees >1200 rpm and closed
> (idle) throttle position switch. Hence the surging.  The way you can verify
> that it is the ISV is to remove it and block the ports and start the car.
> It should idle low. Mine was about 600rpm.

The idle stablisation system on the ur-quattro (and I think the controller is 
pretty common) looks only at the throttle switch to determine whether it should 
be doing anything.  If "yes" (switch closed) it governs the ISV to get 800 rpm 
- unless the vehicle is still moving (speed pulses from ECU) in which case it 
sets 2000rpm for the brake and steering servos, or the battery voltage is low - 
in which case it sets 1200rpm.
 
It also has an "emergency" mode that sets 470ma through the ISV.  In general, 
you can tell what it's trying to do by measuring the current.  430ma is the 
normal base setting for the Bosch ISV.

--
 Phil Payne
 (Temporarily 100012.1660@compuserve.com)
 Committee Member, UK Audi [ur-]quattro Owners Club