90 CQ idle stumble

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Feb 22, 2012 | 09:33 AM

audidrvr

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90 CQ idle stumble

I have been working on an idle issue on my coupe quattro for a little while now and although it has improved it still likes to stumble every so often when sitting at idle or letting of the throttle while driving. I have cleaned the ISV at least 5 times and the last time involved soaking it for an hour and then blasting it some more. I have cleaned the throttle body too. This made things better as it doesnt stall out any more but still isnt right. I read somewhere (20v.org i think) that you can unplug the ISV and the car should idle at its set idle point (ideally ~700-750 rpms) but my car will just die if I unplug the ISV. I did find a vacuum leak that I addressed but havent been able to find any diagrams for the 7a 20v that shows a full diagram of the proper vacuum line routing. I was reading on here today that the EGR valve can act up to so i was going to go through and clean up more stuff and replace more vac lines but would like a diagram as there are some oddities on this car. I also found the process to check the fault codes so i will do that as well.

Any thoughts?

Feb 23, 2012 | 05:40 PM

Solid20vq

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Joined: Feb 2012

Posts: 125

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From: Ashland Oregon

vacuum circuit diagram

Quote:

Originally Posted by audidrvr

Any thoughts?

Have you checked out audi20v.net, It's the newer version of 20v.org. If you register (for free) you can access their hosted version of the B3 service manual, and print off whatever sheets you need.

I was just doing a quick search, but I found this page under:
Fuel supply-Exhaust Engine electrical:

Name: CQ vacuum.jpg
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