Audi 5000 idle problems

[Tom Christiansen]

John,

>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.

I suspected that as well. But then I took it out and applied +12V to it.
The regulator disc does indeed flop around in there when I apply a voltage.
Without voltage applied, there's a small crack left open.

I can actually make the problem appear by unplugging the ISV.

>2) The throttle position switch. Are you sure the car knows its at
>"idle"

The idle switch is good (0 ohms when closed, infinity when open). The full
throttle switch reads 20 ohms when closed, infinity when open.

>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.

Well, I didn't touch any adjustment screws, so unless cleaning the ISV
provoked something else, the settings should be good. But once the car runs
normally again, I'll adjust the mixture to 27% duty cycle on the ISV as
directed on HUW's audi pages.


Thanks,

         Tom