Date: Wed, 11 Aug 2010 21:41:16 -0700
Reply-To: Karl Wolz <wolzphoto@Q.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Karl Wolz <wolzphoto@Q.COM>
Subject: Re: AFM track cleaning wisdom
In-Reply-To: <4C632B1E.5050002@gmail.com>
Content-Type: text/plain; charset="us-ascii"
IIRC, you have an '85? I was told that the capacitor fix only worked on the
digifant system, so if you have the original digijet 1.9L, the capacitor fix
will do you no good. My engine used to cut out just as you're describing,
especially after a long high speed run or after a stiff limb (or during).
Quite aggravating. We never did find the reason for the cutting out, but it
is well chronicled at VW dealerships, though most have probably forgotten
the issue by now.
One dealership mechanic was convinced that the problem (which occurred while
the van was still under warranty) was poor grounding; he installed one
ground strap after another, to no avail. We replace the ECU, the AFM,
countless ground straps and other electronic parts. Eventually, we replaced
the entire engine and the problem went away. No one was ever able to
adequately diagnose the issue.
Oh yeah, we did clean the wiper track in the AFM - no joy there either.
Sorry,
Karl Wolz
|-----Original Message-----
|From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
|Mike "Rocket J Squirrel"
|Sent: Wednesday, August 11, 2010 3:59 PM
|To: vanagon@GERRY.VANAGON.COM
|Subject: Re: AFM track cleaning wisdom
|
|As I mentioned, I had the thing open a few years ago and moved the wiper
|to a fresh portion of the track. I did this as you describe: by ovaling
|the mounting holes, so I phrased it wrong, I didn't move the wiper but
|the track. My bad.
|
|I've only put about 15,000 miles on the thing since, I doubt the wiper
|has worn through the new portion of the track yet. But I will inspect
|and report.
|
|I'm following up on the mechanic's suggestion as he felt that the
|symptoms I described last week (see "Mystery engine cutouts") may be due
|to a bit of schmutz on the track.
|
|Anyway, in Ye Olde Days when I was a broadcast engineer, we used to
|clean the Shallco program attenuators (coined-silver contacts) with
|Hoppe's gun oil. That's probably a bit gummy for a AFM potentiometer,
|but there may be some other cleaner/preservative I can put on the track
|while I have it open.
|
|Mike S and David-The-B both point out that abrading the track with a
|pencil eraser is dumb, dumb, dumb. Point taken. See their posts for
|details.
|
|To David, thanks for mentioning that capacitor -- yes, I have a 22uF
|tant cap wired in to reduce wiper/track noise.
|
|Just for the record, Richard-K asks for general AFM track servicing
|information and says that he has "some `bogging' problems similar to"
|me. I want to say to Richard that I would not describe the problem I had
|as "bogging," more like an abrupt loss of power, mixture slamming toward
|full lean condition, ignition continuing, then after 3 to 4 seconds,
|abrupt return of full power.
|
|Out of curiosity, does anyone know what the ECU tells the engine to do
|if the AFM wiper loses contact with the track? Cut off fuel?
|
|--
|Rocky J Squirrel
|84 Westfalia: Mellow Yellow ("The Electrical Banana")
|74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
|Bend, OR
|KG6RCR
|
|
|
|Tom Young wrote:
|> As I recall, and I may be wrong, the issue here with the AFM track isn't
|> that it's dirty, it's that hours and hours of wear and tear at a
|> particular spot actually result in the surface material being etched
|> away, causing the ECU to think "Oh, the AFM's vane is closed!" and
|> reacting accordingly. So I'm not sure that cleaning has much to offer
|> here.
|>
|> I've had good results by opening up the AFM (air-cooled, and I'm
|> assuming the water-cooled engine's AFMs are the same), removing the 4
|> screws that hold the wiper circuit board, removing the circuit board
|> itself and then ovalizing the 4 holes in the board that the screws pass
|> through. You can then re-install the circuit board in just a slightly
|> different position, giving the wiper a new track to pass over.
|>
|> Tom Young
|>
|>
|> ----- Original Message ----- From: "Mike "Rocket J Squirrel""
|> <camping.elliott@GMAIL.COM>
|> To: <vanagon@GERRY.VANAGON.COM>
|> Sent: Wednesday, August 11, 2010 2:30 PM
|> Subject: AFM track cleaning wisdom
|>
|>
|>> My mechanic dude suggested the the cause of the engine's periodic but
|>> brief loss of power during grade climbs last week might be a dirty spot
|>> on the AFM track and suggested gently cleaning it with a pencil eraser.
|>>
|>> I opened it once before, a few years ago, to move the wiper to a fresh
|>> bit of track. I'll open it again to clean the track.
|>>
|>> Is the pencil eraser trick good enough, or would it benefit to use some
|>> kinda cleaner?
|>>
|>> --
|>> Rocky J Squirrel
|>> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
|>> 74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
|>> Bend, OR
|>> KG6RCR
|>>
|>
| 
