See if you can't find an article written by hugie_at_lindy.stanford.edu
posted June 13, 1994 entitled "1981 Van running rich, FI problems SOLVED" in
the archives.  It may explain the problem.
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Tom Young
Lafayette, CA 94549
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----- Original Message -----
From: "vanagon" <vanagon@MAIL.ABSOLUTEARTS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, October 13, 2006 9:02 AM
Subject: 89 backfires, sputters when warm. MYSTERY problem!!

>I am reposting this question because NOBODY has been able to fix it!
>
> I have been completely clueless for almost a year by now about my 89
> Vanagon.
> I have never had a problem with this it and rebuilt the engine about 3k
> ago.
> It ran beautifully until one day it just stopped running right.
>
> It idles and accelerates fine when cold. Just as it gets warm it starts
> coughing and backfiring through the air intake when you press on the gas
> like
> if you would accelerate from a red light. It sounds like it is not getting
> the
> right mixture. It smells weird. It just won't smoothly accelerate and rev
> up.
> You obviously cannot drive the van this way. It will hesitate like crazy,
> sometimes it will backfire through the air intake other times it will rev
> up
> a little.
>
> The computer will reset itself and it will run fine for about 30 seconds
> when
> quickly turning off the ignition and back on again. IT IS NOT A mechanical
> issue because compression and all are fine.
>
> All electrical test as per official service manual check out fine,
> computer
> checks out fine, new o2 sensor, fuel pressure fine, injectors brand new,
> coil
> brand new, distributor brand new, temp sensors new, grounds to chasis
> fine,
> all resistance tests are fine, relays like fuel, etc. test fine, new
> plugs,
> wires all new, new gasoline as well... It must be electrical but where???
>
> Of course when grounding the o2 sensor the motor will run because it
> enriches
> the mixture... but when hooked up correctly it will not. continuity
> between o2
> sensor and brain is fine, too. resistance of o2 sensor is fine, too. temp
> sensor at intake is fine as well,
>
> Does anyone have an idea what this problem is???  NOBODY seems to know
> what
> the problem is... I wonder if we have a real expert here!!!