Idle Hunting - '87 5kcstqw

[Smeins, Larry]

Replacing the ISV fixed a similar problem on my 5kcst.  You can isolate it
to the ISV with two checks.  You've done the first by removing the ISV
connector with no change.  That should eliminate electrics. Next remove the
ISV outlet pipe, the one between ISV and intake manifold, and block it by
placing  a sheet of plastic, a double layer of sandwich bag works, over the
ISV outlet and sliding the pipe back on.  Start the engine and see if the
problem still exists.  The engine should idle quite low, mine idled between
4 and 5 hundred.  If the problem goes away its a leaking ISV.  

Larry from Loveland, CO

>From: "Swann, Benjamin R.  (BSWANN)" <BSWANN at arinc.com>

>I'm sorting out issues with the new to me 5000 Turbo Quattro Avant.  This
>problem cropped up while I was driving it back from Georgia to MD.  The car
>began surging while I was driving it and slowed to speeds under 50 MPH.

>I am trying to isolate culprit - engine is hunting for idle, revving to
>about 1500RPM then dropping down to around 700 repeating about 1/sec.