It is a small leak in your exhaust problem.  I experienced the same thing
until I replaced my exhaust system.

Bradley Flubacher
State College, PA
'82 VW diesel westy
'84 GL wasserboxer

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
Of John Schaper
Sent: Tuesday, May 08, 2001 10:39 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Back-fire

In my 85 GL on Sunday, I was driving down from Sonora Pass when I experience
the engine backfiring going downhill, rpm's at 4,000, coasting.  I have a
small leak in my exhause, upstream from the O2 sensor.  Is this a timing
thing?