Re: Coupe Quattro 20V ISV question

["J. Graham McGowan" <escoses@earthlink.net>]

jgraham1@erols.com wrote:

> Peter Schulz wrote:
>
> > Folks:
> >
> > My 1990 Coupe Quattro is going through a habit of stalling and
> > irregular idling.  While driving, and then for instance, taking
> > the car out of gear to stop, the rpms will drop to 500 or below,
> > causing the motor to buck, sometimes stall, sometimes return to 900.
>
> >
> > I replaced the ISV two years ago, and I recently replaced the old
> > rubber crankcase breather with the upgraded metal replacement.
> > Cap, rotor, plugs, plug wires were replaced last year.
> >
> > I always run the CQ on Texaco 93 octane. As a test, I disconnected
> > the ISV lead, and the engine promptly died.  The engine would not
> > start with the ISV lead disconnected.
> >
> > I removed the ISV, and cleaned it with carburetor cleaner, and then
> > thoroughly with brake cleaner with that ran out. After the ISV
> dried,
> > I reconnected it, along with the lead.
> >
> > The engine idled better for a while, then returned to its old
> habits.
> >
> > This problem seems to be accentuated by hot, humid weather.
> >
> > Any ideas?
> >
> > Thanks!
> >
> > Peter Schulz
> > 1990 Coupe Quattro
> > schulz@ed.ray.com
>
>  What type of spark plugs are you useing? I find that my CQ 20V will
> not
> run right with
> anything other than the factory plugs F6DTC.
>
> John.
> 1990 QC

 It probably has nothing to do with the plugs, although having good
clean, properly gapped plugs won't hurt. More likely it is a combination
of the ISV, O2 Sensor and the Air Mass Sensor.
Downloading the fault codes should tell you what the problem is.

My contribution,

Graham