Date:         Tue, 30 Sep 2003 13:28:26 -0700
Reply-To:     Harald Rust <harald_nancy_vw@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Harald Rust <harald_nancy_vw@YAHOO.COM>
Subject:      Re: The "Other" Vanagon Syndrome, Part II
Content-Type: text/plain; charset=us-ascii

James,
I found the cap fix to help when I soldered it in the
afm. That's already years ago, and all my afms have
the cap in them. :-)
But the cap, of course, doesn't fix everything,
and I don't think it will cure a worn out afm track.
I experienced intermittent vs while using a new Bosch
rebuilt afm a few years ago while on a trip.
After that I soldered in the cap.
That former intermittent vs wasn't as bad as what I
just experienced going to and from Yellowstone.
On this trip I was lucky enough to have the digitool
along, and be able to watch the voltage signal
from the afm to the ecu while the vanagon was
stumbling. The number I saw on the digitool lcd
for the afm would be something like 3.54 while
cruising around 60, which is a normal reading.
While keeping the accelerator steady, only the last
digit on that number would change, like to 3.52 or so
and then back to 3.55.
A very steady signal, no wild fluctuations.
As the vanagon would loose power, the afm reading,
of course, would get lower, as the engine sucked in
less air. The signal went down steadily and evenly
to about 2.94, never fading out or anything.
To me that indicates the afm track was working
properly, and the ecu was receiving a good steady
signal from the afm.
Meanwhile during the stumbling, the O2 sensor signal
as registered on the digitool would go into the
negative reading, indicating a leaning out of the fuel
mix while the afm signal was still steady.
Imho something else was causing the loss of power.
About cruise control:
I had the same experience using the cruise control,
as you described.
In my case I suspected clogged fuel injectors not
injecting enough gas causing the fuel mix to lean out,

and the vanagon to slow down.
As the vanagon slows down due to the lean fuel mix,
the cruise control opens up the throttle, trying to
compensate for the loss of speed.
This would make the fuel mix more lean, and the
vanagon
stumbles worse.
It was better to turn the cruise control off.
When a bout of stumbling would occur, I took my foot
off the accelerator. This would make the vanagon run
better again, albeit slower.
Giving gas would make the stumbling worse.
Of course, being back home, the vanagon runs
perfectly,
freeway or in town.
I still think the vanagon and the wbx with the factory
setup is quite reliable. The main reason we had this
problem on our last trip is just due to the fact that
we use our vanagon camper so much that the miles just
accumulate.
So in my case I wouldn't be surprised if the fuel
injectors are working at less than optimum
performance.
I'm going to put in a new set of injectors, and take
another trip, and see if it runs better, but I might
also take a spare afm along next time.
Harald
'90 westy
James wrote:
Coincidentally... I just returned from a trip to
Yellowstone (from so cal)
as well, and had a similar experience.
On the way there, the van ran fine for the first 300
mi.  Then, north of Vegas the bucking began.  Slowly
progressing until it died on the highway.
Turning it off, then on would cure it for a time.
Having left my brand new spare AFM at home (!), I had
similar thoughts of bad gas and such and dumped
a bottle of fuel cleaner in and poked the engine at
the next gas station. No dice, of course.
Got to Yellowstone and drove all over the park - a few
hundred miles - No problems at all.  I thought the
problem was somehow fixed, and was expecting a leisure
ride home.
But just towards the end of the first day of the
return trip (500 mi), the problem returned.  The thing
that I noticed and from what I've read, the
problem manifests after a long period of cruising,
(I'd usually have the cruise control on).

So, on the second day of the return trip, I varied my
speed, usually between 65 and 75 the entire way home.
I'd still use the cruise, but I'd cancel it
every 15 min or so and change speed and/or let off the
gas completely and/or de-clutch to drop the revs for a
couple of seconds.  I didn't experience the
problem at all that day - 500 mi of straight highway
driving.  Now that I'm
back home to city/fwy driving, it's been fine.
I'm fairly certain my problem is AFM related - I don't
have the capacitor fix.  Which brings me to my
questions:
Is the vanagon syndrome caused by a
non-capacitor-fixed AFM or simply a bad AFM, or
either, or both?  Had I swapped out my AFM for the new
one, would I
be just as likely to experience the problem, since it
wasn't "fixed"?  And what exactly is happening that
makes the AFM go nutty???!
Thanks,
James
90 Carat


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