Likewise, desert-like terrains. Roughly mid-Nevada Hwy 50 after the longest, straightest, flat run of that long trip with an AFM with < 5000 mi. Textbook case. I have always assumed a harmonic vibration resonance not unlike the VW Tech Bulletin 92-01. I have since added the capacitor fix but not repeated that same Hwy 50 test. Yet. My family insists on recharged ac before any more desert trips. Coastal weaklings. Philip Chidlaw Gualala, CA -----Original Message----- From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of Harald Rust Sent: Tuesday, September 30, 2003 6:24 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: The "Other" Vanagon Syndrome, Part II
The afm-caused intermittent syndrome has been an enigma. Volkswagen designed the harness as a fix, and dealers have installed it on good afms. The afm harness is not supposed to fix a worn out air flow meter. It is supposed to stop the intermittent bucking/stalling syndrome. That syndrome has nothing to do with a worn out afm, but a worn out afm could cause it as well. There has been much speculation as to the cause of afm-induced intermittent syndrome. I wouldn't be surprised if even Volkswagen doesn't exactly know the cause of the erratic behavior of some afms. Some speculate that it's the air flow meter flap oscillating as the air flows through. If the flap starts vibrating, it could send an erractic signal to the ecu, which would make the ecu shut down until it's reset by turning off and restarting. Another cause could be static electricity building up, maybe due to the air flow through the afm. Static could send erractic signals to the ecu, causing the bucking. I have only noticed the intermittent syndrome in desert like terrains. That made me think of static buildup around the afm. The cap seemed to fix that. Another cause probably could be a worn afm resistor board, but that should be easier to detect and replace the afm. You can also easily test the afm with a multimeter, as according to Bentley. Harald '90 westy James wrote: Thanks for the explanations. The decriptions as a potentiometer makes it clearer to me. What I still don't understand is, why the problem only manifests after sustained cruising. Why doesn't the van always stumble when the AFM crosses the "bad contact" point? I cruise control to work for 20 minutes and have never had the problem. Yet, after a few hours of similar cruising on the road trip, it happened. Not that any of this theory matters, really - just curious. James 90 Carat
__________________________________ Do you Yahoo!? The New Yahoo! Shopping - with improved product search http://shopping.yahoo.com |
Please note - During the past 17 years of operation, several gigabytes of
Vanagon mail messages have been archived. Searching the entire collection
will take up to five minutes to complete. Please be patient!
Return to the archives @ gerry.vanagon.com
The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.
Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.