Kim Brennan once stated in a list email or a pmail to me that he had
seen the insides of the VW AFM harness and it had more electronics in it
than just a capacitor. He didn't elaborate and I assumed that this was
correct.    IIRC,  both work to smooth out the signal from the AFM to
the ECU so that the ECU gets a steady signal and doesn't cut out from
thinking the lack of a signal from the AFM or from getting one outside
the operational parameters.   AFM's can get worn spots on the track
which are essentially a dead spot from which no signal, or an aberrant
signal, is generated.  Signals outside the operational parameters can
cause the ECU to stop the signals necessary to operate the van, hence it
cuts out for a brief period (or longer with some other problems).  This
can also be fixed by moving a board inside the AFM so that the moving
arm tracks on a different part of the board making an arc without
passing over worn spots.

A number of folks have used both the capacitor fix and / or the VW
harness and found that it didn't solve their van's "bucking" problem.
Many times a bucking, or intermittent operation, problem is not caused
by the AFM, and therefore, doing something to the AFM will not eliminate
the problem.   It can be a vacuum leak, or a problem with another sensor
in the FI system - e.g., the Temp II sensor, the O2 sensor, the idle
control unit, etc.

Similarly, if the O2 sensor is not the cause of an operational problem,
then replacing the O2 sensor will not fix the problem.  You have to
replace the part(s) responsible for the problem.

Careful attention to the exact circumstances under which the
intermittent operation comes and goes helps to identify which component
has failed or is failing.  However, sometimes it is something as simple
as a faulty ground connection or bad wiring to a component such as the
O2 sensor.

I cannot remember anyone reporting that the capacitor fix did not work,
but that the bucking problem was then cured when they used the VW
harness, having made no other changes to the FI and ignition systems.
My memory could be wrong, but I try to pay close attention to posts of
that nature.  Maybe someone has had or remembers a report of a contrary
experience.

Sam

Sam Walters
Baltimore, MD

89 Syncro GL
85 Westy Weekender

All incoming and outgoing email scanned by
automatically updated copy of Norton AntiVirus.