Audi 5000 idle problems

[John Sherrow]

I would suspect:
1) The ISV. I know you just cleaned it but the symptoms you describe are
consistent with an ISV that is allowing engine vacuum to pull air past
the regulator disk. I think there is an "idle/rpm" cut off which is why
the rpm drops back down at 1600.
2) The throttle position switch. Are you sure the car knows its at
"idle"
3) The Idle Setting. I had my engine do this once when I was fooling
with the idle setting and had too much air coming thru the throttle
screw. I backed the idle screw in and the problem stopped. Not sure
about the root cause.