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Date:         Mon, 28 Jan 2002 01:04:01 -0500
Reply-To:     Laurence Smith <lsmith@COGECO.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Laurence Smith <lsmith@COGECO.CA>
Subject:      Persistent running rich problem finally fixed.  Here's how.
Content-Type: text/plain; charset="iso-8859-1"

Hello List,

After nearly 4 months of fiddling I have finally solved my rich running condition on my 90 Westy. Perhaps my fix will help someone else.

As background here is (was) the main symptom: * running very, very, very, rich after warm up, van not driveable, billowing black smoke * when warm, engine running, remove TempII wire, or AFM pigtail sets the computer into open loop and rich condition went away * disconnecting O2 sensor did nothing

Attempted fixes: * replaced TempII, ECU, AFM, O2 sensor, fuel pressure regulator, all injectors, ignition wires, plugs, cap, rotor, idle stabilizer control, ignition switch (I was desparate) * continuity in ALL wiring was good * rebuilt throttle body & idle switch, cleaned idle stabilzer valve, checked all vacuum lines, checked all connectors, adjusted timing, tested Hall sender * replaced battery and engine block big grounds, soldered all 7 engine ground wires with new eyelets, added a ground to the AFM and the right side of the engine.

NOTHING WORKED! VAN NOT DRIVEABLE FOR 4 MONTHS.

Dave Homer (London, ON) of this list was kind enough to pop over to my house and help out. He changed this and that but admitted this was a tough one. David Beierl in NJ, also on this list, helped me out on the phone. Many others on this list e-mailed me suggestions. Joel Waker, on this list, spent time writing me an extensive e-mail with suggestions. Thanks to all for your help.

The solution: * On the Digifant ECU terminal 19 there is a brown/black wire that grounds the green O2 sensor outer wire jacket. It is brown/black on the 90 Vanagon, but is a different brown combination on other years (says Bentley). * This wire was missing in my engine compartment. It was no where to be found. Not peeking out of the harness, or under some crud. It was gone. The previous owner (July 2001) must have snipped it off. Who knows. * I have no idea how the van drove acceptably August-September but it did. Perhaps an internal ground in the harness. * To fix it I stripped back the harness connector at the ECU, attached a ground wire to the brown/black wire and led it back to the engine and grounded it. Voila problem gone. Runs great! For fun, I removed this ground and the black smoke appeared again.

What I have learned: * Review the Bentley wire diagrams. Really, really review them. Learn all the wires that should be there. The diagrams are extremely accurate. * Trust the resistence and voltage specs in Bentley. Don't second guess them. EXCEPT: Adding the AFM Vanagon Syndrome pigtail harness changes the Bentley test procedure for the AFM. A VW Technicial Service Bulletin mentions this. * Be methodical about testing every Digifant component. Don't ignore any of them. * Find a friend that can swap out Digifant components. * The O2 sensor, its connector to the green coax, the impedence this sets up, and how the ECU interprets volts when warm is extremely important. I was under the false assumption that if the O2 sensor was disconnected, there was no influence on the ECU. Wrongo!

I hope no one else goes through the pain and money I have had to endure for a simple missing ground wire.

Laurence Smith Hamilton, ON 90 Westy (fanumbos)


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