Date: Sun, 16 Jan 2005 17:07:49 -0800
Reply-To: David Marshall <mailinglist@FASTFORWARD.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <mailinglist@FASTFORWARD.CA>
Subject: Re: capacitor fix mitigated buck, did not fix
In-Reply-To: <8965f792cd5.41ea923c@ou.edu>
Content-Type: text/plain; charset="us-ascii"
The capacitor is NOT a fix, it is a band-aid to the problem. If you pop the
black plastic cap off the Air Flow Meter, you will see a circuit board that
an arm sweeps across. The more air that goes through the AFM, the farther
along the variable resistor this arm goes. Picture turning up the volume on
your radio, more air turn up the "volume" on your engine sort of speak.
Anyhow, the problem is that over time, this arm wears though the resistive
surface and eventually you get some dead spots. The computer gets confused
on these dead spots and it creates this bucking problem. The capacitor,
fills in the gaps in the signal as it stores voltage. After a while there
will be so much of a gap created that the capacitor can no longer smooth
things out and you will get a bucking problem again. The factory pigtail
thing will give the same problem. The simplest fix which is cheaper and
better than the capacitor is to give the arm a little "tweak" so that it
goes across a new track on the resistive surface. Just make sure that when
you give it a little tweak that you don't twist it as it will lift off the
resistive during certain parts of the arc that it travels. Last summer my
112hp 2.1L wasserboxer started bucking like crazy. The side of the road
with a Swiss Tool to pop the cover off and a small tweak later I was in
business - 10,000km later not a hint of problems. Just make sure that you
seal the black plastic cover on so that you don't get water in there.
David Marshall
Fast Forward Automotive Inc.
4356 Quesnel-Hixon Road
Quesnel BC Canada V2J 6Z3
http://www.fastforward.ca mailto:sales@fastforward.ca
Phone: (250) 992 7775 FAX: (250) 992 1160
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-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
Of Warren Lail
Sent: January 16, 2005 2:12 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"