Date:         Thu, 10 Aug 2006 19:07:18 -0400
Reply-To:     Kenneth Lewis <kdlewis@NORTHSTATE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Kenneth Lewis <kdlewis@NORTHSTATE.NET>
Subject:      Re: 1000 mile rebuild recommendations?
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
              reply-type=response

Michael,
   Just because the AFM is rebuilt doesn't mean it's good. Possibly the
spring is not tensioned correctly. I wish there was a good procedure out
there to tune them. Here are some things I have learned by experimentation.
YMMV.

   First you need a good voltmeter and O2 sensor. The three throttle body
alignments outlined in the Bentley should be checked. Carefully pry the
black cap off . If you don't mess it up too bad it will go back on and stay
without glue. Drill out the plug so the allen screw is accessible. Use an
allen wrench and determine the base setting of the allen screw. That is,
find out how many turns until it bottoms out so you can return to where you
started, just in case. Write it down. Likewise mark the black plastic wheel
so you can return it to it's original starting place.
   The engine has to be up to operating temperature. Disconnect the O2
sensor and hook up the voltmeter to it. If it is running lean the reading
should be near zero. Ideally the voltage should toggle equally between zero
and (about) one volt.
   Off the top of my head I can not remember which way to turn the wheel to
enrich the mixture. I noticed that after a few notches in the right
direction the engine RPMs picked up and smoothed out. Unfortunately the
spring tension that equated to the best sounding idle did not give the best
reading from the O2 sensor. This is the part where I wish I had a good
procedure written out. I fiddled with the spring tension and idle screw (on
the throttle body) until I got a happy balance between idle and good O2
sensor output. Use the allen screw to fine tune the O2 output voltage.
Hopefully the output is good at higher RPMs, otherwise you need to adjust
for that.
   I run through this procedure every year before vehicle emissions testing.
Good Luck,
Ken Lewis
http://neksiwel.20m.com/ (more O2 info here)