Date:         Mon, 9 Oct 95 15:56:55 PDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Dave Kautz <dkautz@hpsidms1.sid.hp.com>
Subject:      Missing from Bentley

  This message is likely to be of interest only to folks owning mid-70s
  breadloaves or to techno-geeks who have their emission equipment still
  hooked up...the rest of you can prevent the onset of nausea by pressing
  the delete key now.

  As those of you who read EVERY SINGLE POST may remember that the guilt
  of environmental destruction was weighing heavily on me a week or two
  ago resulting in the awakening from hibernation of my EGR valve. As I
  mentioned at the time, this resulted in a mid-range stumble that was
  particularly annoying when the engine was cold.          

  I found myself mumbling that there is no way that the engineers at VW
  would have shipped something that ran like this and that there must
  be something wrong. The other evening I gathered my stack of service 
  manuals and read everything I could find on the EGR system.

  In one of the diagrams in Haynes, which has some errors otherwise, I
  found a reference to an extra vacuum line used on California spec. 
  carbureted engines which have a two stage EGR valve instead of the
  "plain jane" model used in the other 49 states. Bentley, and I re-read
  it carefully, makes NO mention of this. 

  Now I have always wondered why I had an extra tube sticking out of the
  right hand carb and it suddenly became clear to me how this thing was
  supposed to be plumbed up.

  So here's how it goes, if you've got the same setup: The vacuum line from
  the brake booster circuit goes to the single fitting on the right hand
  side of the EGR solenoid control valve. The "extra" vacuum advance tube on 
  the right hand carburetor gets connected to the lower tube on the left side
  of the EGR solenoid. The upper tube on the left side of the EGR solenoid
  goes to the EGR valve. 

  I think it's okay to use the vacuum advance port on the left hand carb
  for the EGR <it's a lot closer> and the one on the right for the distributor
  if you want - I tried it both ways and it seemed to work the same.

  And yes, this does get rid of the stumble. I suspect that the stumble was
  caused by the abrupt change in manifold vacuum when the EGR was suddenly
  fully opened to it's second stage position by the microswitch on the 
  throttle linkage. With it plumbed correctly it is opened slightly,
  to the first stage, by the vacuum from the throttle plate
  resulting in a smoother transition to second stage when triggered by 
  the microswitch.

  I realize that this all sounds very complicated and confusing. If anyone
  would like more clarification, send me some email at dkautz@hpsidms1.sid.
  hp.com and I'll try for a better explanation or a diagram.

  Regards,

  Dave