Date:         Mon, 10 Oct 94 9:55:53 PDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Steve Johnson <sjohnson@pcocd2.intel.com>
Subject:      Digifant problems - uneven running 

So Edward Wilson says:
> From root Mon Oct 10 09:41:28 1994
> Date: Mon, 10 Oct 94 11:38:51 CDT
> Message-Id: <9410101639.AA02274@northstar.Stanford.EDU>
> Errors-To: gsker@lenti.med.umn.edu
> Reply-To: vanagon@lenti.med.umn.edu
> Originator: vanagon@lenti.med.umn.edu
> Sender: vanagon@lenti.med.umn.edu
> Precedence: bulk
> From: Edward Wilson <ed@sun-valley.stanford.edu>
> To: Multiple recipients of list <vanagon@lenti.med.umn.edu>
> Subject: Digifant problems - uneven running 
> X-Listprocessor-Version: 6.0c -- ListProcessor by Anastasios Kotsikonas
> 
> 
> Hi, 
> I'm having some problems with my girlfriend's '92 Golf (Digifant II
> Fuel injection), that seem to be almost the same as my Dad is having
> with his '90 Vanagon.
> 
> Problem:  The car was running fine, we had been on the freeway for ~45
> minutes, then suddenly it started to stumble (as if the fuel were being
> cut off), we turned around and made it home - it seemed to run better
> the faster we went (3500 rpm+), but would still stumble every few
> seconds.  The car is barely driveable at lower rpm.  With the car
> stopped, and out of gear, if I hold my foot on the gas at a fixed
> point, the rpms will vary chaotically from idle to 2500.
> 
> It had done the exact same thing 2 weeks ago, just as we arrived at
> Lake Tahoe (~6000 feet elevation), so I changed the fuel filter (didn't
> seem too dirty), and the problem gradually went away after about 5
> miles of driving.  I thought it was solved, until now.
> 
> My dad's problem:  My parents just finished driving from Pennsylvania
> to Washington State, and they had some trouble going through Wyoming at
> 4000 foot elevation.  They went through the same drill as I did:
> problem happened, change fuel filter, problem goes away, several
> hundred miles down the road (still in Wyoming - it's pretty big), the
> problem shows up again.  Fortunately, they found someone who knew about
> VWs, and he asked my Dad if they had "a resistor".  My dad said he
> didn't think so, so they explained what it is:
> 
> VW part number 025 906 302 A - costs $95 (in Wyoming).
> This is a wiring harness with a male connector on one end, and female
> on the other that attaches to the air flow sensor (in-line with the
> existing circuit).  The mechanic said that almost all the Vanagons in
> the area had this (due to high altitude?).  My Dad drove the bus until
> the problem showed up, pulled over, slapped this in, and it went away,
> so he's convinced it works.  Does anyone out there have this
> "resistor", or have any clues?

I don't have it yet, but I can tell you that it is NOT covered under
warrantee :(  (Bad P.R. IMO).  Altitude has nothing to do with the
cause of this problem.  VW explains in their Tech. Bulletin 92-01
that the cause is that "some air-flow meters experience a vibration
resonance of the metering potentiometer wiper during extended constant
driving.  This resonance causes the air-flow meter to supply an inter-
mittent signal to the Digifant ECU.  The ECU will then default to a
"no-load" condition and reduce the injection time."

It doesn't say how the harness (part No. 025 906 302) fixes this problem,
but apparently it does in most vanagons.

I don't know if this applies to the Golf either.

Steven

sjohnson@pcocd2.intel.com