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"