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Thu Nov 20 15:09:11 EST 2003

time. Yes? If not, they could be multiple problems.

When boost pressure drops like you describe, suspect a leak somewhere in the
boost tract. It is rather common as rubber tubes come loose or get old and
start to leak. Finding leaks can be a PITA so I bit the bullet and built a
pressure tester.

Ted suggested it might be a leak at the BPV. I think it might also be as
leak at the ISV (idle stabilizer valve). I will explain where the little
nipper is. The ISV is a metal cylinder about 3" long. It is mounted just aft
of the throttle body so it is easy to reach and check.

To be perfectly honest, I have never really looked for the BPV on my car. If
you find it, clue me.


-----Original Message-----
From: 200q20v-admin at [mailto:200q20v-admin at]On
Behalf Of Holbrook at Associates
Sent: den 17 maj 2003 23:54
To: 200q20v at
Cc: theholbrooks at
Subject: boost instability

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I have a 91 20v quattro and have been experiencing a couple problems.The
main one has to do with the turbo boost pressure going up to a peak of about
18psi and as it peaks it will then drop of and occilate back between about
13 and 18 psi. You notice a surging of acceleration along the way.Also
recently it has been stalling when you let off the throttle after reving it
at high rpm. To keep from stalling you have to get on the gas and ease it
back to idle. Any info would appreciate much.  Steve Holbrook

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