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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
Comments: To: wlail@OU.EDU
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"


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