Date: Sat, 8 Jul 2006 10:38:10 -0700
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Followup to: Which "surging syndrome" is this one?
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For the archives:
Toward the end of last month I requested help diagnosing a loss of
power/surging syndrome that Mellow Yellow exhibited when we were
climbing up a long grade to over 5,000 feet. I was in second gear (auto
trans) and running at a moderately high rpm, maybe 3500. Every 60
seconds (or so), the engine would suddenly lose power as if I had taken
my foot off the gas. The "power outage" would last for a few seconds,
maybe 5, then the engine would cheerfully resume. This occurred repeatedly.
Upon the advice of the group, I did the following:
1. Per Roger Sisler's suggestion, I opened up the AFM and loosened the
three screws holding the circuit board*, and slid the circuit board
closer toward the rear of the van. The wiper contacts had worn deep
grooves in the resistive element, and by moving the circuit board, the
wiper had a new element surface to work on. That oughta last another
70,000 miles (current mileage on Mellow Yellow).
2. On the trip I had heard a hissing noise under/around the rear of the
van. Snooping around with a bit of garden hose to my ear localized the
noise to where the throttle body mated to the air distributor. It's a
total PITA to get a screwdriver in there, but somehow I managed to
tighten the two bolts so that the leak was closed. Someone p-mailed me
about how a leak here could have caused the loss of power, and I'll be
darned if I can find that p-mail to publicly thank him.
Results: Last week we took the van on another trip, with a similar
climb, and the symptom seems to be eliminated. If I'd had more time for
scientific endeavors I'd have liked to have made one correction at a
time to learn what the real cause was. But the resistive element in the
AFM was clearly worn, so correcting that was probably not a bad idea.
The air leak couldn't have made the engine run better, so it needed to
be done.
Many thanks to all for troubleshooting tips. I wish I was more
knowledgeable so I could contribute as much as y'alls.
*WARNING: The three screws are "tri-round" thread-forming screws with a
triangular cross-section (http://www.callhpfs.com/prod01.htm) and VW
applied a thread-locking adhesive to them at the factory. It might be
possible to loosen these screws with a perfectly-shaped Phillips driver,
but I pretty much destroyed the head of one of them trying to loosen it.
I was able to get it out by grabbing the head with a pair of narrow
Vice-Grips, and found a suitable replacement at my local hardware store.
I have no idea why VW felt this board needed to be affixed so securely.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
