Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (February 2000, week 2)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Wed, 9 Feb 2000 13:45:33 -0500
Reply-To:     David Beierl <dbeierl@IBM.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@IBM.NET>
Subject:      Re: 87 Van Bucking (Solution...?)
Comments: To: Steven Shane <s.shane@POBOX.COM>
In-Reply-To:  <vanagon%2000020913115534@GERRY.VANAGON.COM>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 01:03 PM 2/9/2000 -0500, Steven Shane wrote: >For details on the infamous Vanagon "BUCKING" problem, see Ken's email from >Jan 7th below. > >Anyway, the problem is not that uncommon and it can be resolved by a small >device issued from VW specifically for this problem. Eric, my mechanic was >telling me there is even a TECHNOTE issued from VW about this problem and >device, so maybe someone with pull can find this Doc and post the juicy bits >to the list.

There are lots of things that can cause engine misbehavior, including a bad AFM. The VW device is *intended* to cure a problem with a supposedly good AFM, where in a long period of driving at a steady speed the the ECU gets confused by (supposedly normal) oscillations from the AFM and panics, resulting in loss of power (but not bucking) which is cured by turning the ignition off and on again (thus resetting the ECU).

It may also help situations (common by now) where the AFM is worn and causing spikes in the signal.

It is an active IC low-pass filter that limits how rapidly the signal from the AFM can change.

>Anyway, this electronic device (estimated around $80 - $100) inserts between

They were $75 when introduced -- now they are about $175.

Many people have had success by installing a 22 uF 35v tantalum capacitor across the AFM active leads, cost about $2.50 plus your time and solder.

In the case of a worn AFM, cleaning the carbon track is helpful, as is slightly relocating the board so that the wiper tracks in a different area. You may have to open out the mounting holes a little to move the board, but it only has to move a little -- 1mm maybe? The wiper has two contacts, so you wnat the new tracks to straddle one of the old ones.

A worn AFM can definitely cause poor idle and no doubt highway bucking as well. If replacing it cures the problem, then it was *not* the problem that VW designed the special harness for -- although that harness or the capacitor may well help.

cheers david David Beierl - Providence, RI http://pws.prserv.net/synergy/Vanagon/ '84 Westy "Dutiful Passage" '85 GL "Poor Relation"


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.