Date:         Sun, 16 Jan 2005 19:08:54 -0500
Reply-To:     Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject:      Re: capacitor fix mitigated buck, did not fix
Comments: To: wlail@OU.EDU
In-Reply-To:  <8965f792cd5.41ea923c@ou.edu>
Content-type: text/plain; charset=us-ascii

The effects of those capacitors added on work in the range of milli.
seconds, not 50 miles. It is really a band aid and I believe VW never
really diagnosed the problem. As for false signals and circuit
fluctuations, the real problem is the O2 sensor circuit. When this
happens next time, quickly turn the ignition off and back on even while
the van is still moving. If the problem goes away for 30 to 60 seconds,
the O2 circuit is the problem.

Problems range from a bad O2 sensor, (new only means new, not good),
poor wiring, (that green shielded cable), and a floating/poor ground.
Also, most Vanagons are missing the heat shield/deflector on the O2
sensor. The part # is 035-906-274. This helps deflect wind so the sensor
can stay hot and keep the flood of water and road debris from the left
rear wheel off of it. The O2 sensor also senses outside air, a good
splash of dirt or salt in the right place will destroy it.

Hope this helps,
Dennis


-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Warren Lail
Sent: Sunday, January 16, 2005 5:12 PM
To: vanagon@GERRY.VANAGON.COM
Subject: capacitor fix mitigated buck, did not fix

Hi all,

Maggie and I made a safe and fun trip to New Mexico (1200 miles
roundtrip) and Bill Bones performed well,
sort of...

The dreaded bucking syndrome began so I stopped and soldered in a 15
volt 22 microfarrad tantalum
capacitor that I got from listmember Tom Miller.  I connected the
positive side to number 2 and the negative
side to number 4.  Interestingly, the idle that had always surged, was
now stabilized.  The next 50 miles
were a joy.  No bucking at all.

However, after about an hour on the road, just when the bucking normally
begins, I got a diluted version
of the same thing.  It appears that the capacitor stores energy or
something like that, and when the system
needs it it is returned (not sure about this).  The result was that
instead of a bucking jolt like I normally get,
I got a slow loss of power, and then a return surge.  It is as if the
capacitor is almost powerful enough to
remedy the situation, but not quite.

On the return trip, I got behind the bus and smelled the exhaust.  It
seemed to have that smell associated
with a lean engine.  Not wanting to burn anything up, I disconnected the
capacitor.

Of course, the original bucking returned, as did the high idle (1800 rpm
after coming off the Interstate).
The high idle is never a problem around town.  It only occurs after
extended driving on the Interstate,
and accompanies the bucking behavior.

Several questions:

1.  Is the capacitor really a fix or just a band-aid?
2.  If it is a fix, what did I do wrong?  If a band-aid, what is the
real cause and how can it be remedied?
3.  Will a new AFM solve the problem?
4.  Is the factory pigtail a better fix (albeit a more expensive one)?

As always,  thanks for your help.

Warren Lail
88 Westy "Billy Bones"