----- Original Message -----
From: "Craig Oda" <craigoda@COMMUNITYBUILDERS.INFO>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, September 08, 2003 4:10 PM
Subject: Fuel air mixture or timing adjustment?

> I heard from Karen Davis that her problem with high HC in her CA SMOG
> test was solved at BusLabs with a timing adjustment.  Since her problem
> symptoms were similar to mine, I would like to try and adjust the timing
> or at least check the timing on my 1.9L waterboxer.
>
> How can I try this myself?  Is this documented in the Bentley manual?
> Please advise.

Assuming you have and know how to use a timing light, then checking the
timing is not difficult.  On my air-cooled Vanagon with factory electronic
ignition I have to disconnect the two plugs to the idle stabilizer and
connect the two plugs together before checking timing.  I'm not sure about
the water-cooled Vanagons but I think the early waterboxers have the same
setup.  The Bentley should explain the process.

> Damon Campbell said that BusLabs adjusted the fuel air mixture of his
> 2.3L waterboxer.  Before the adjustment, the symptoms were similar to
> mine.  I would like to try and adjust my fuel-air mixture too.  How can
> I do this?

This is best done at a shop with an exhaust gas analyzer, assuming they
insert the probe *in front* of the catalytic converter, not up the tailpipe.
However, if you have a voltmeter and a good O2 sensor you can do a fairly
accurate adjustment as follows:

1)Drive vehicle to get everything completely warmed up.
2)Stop engine, disconnect the signal wire from the O2 sensor (don't know if
you have a 3-wire or 1-wire O2 sensor in those things) and connect the
voltmeter to the O2 sensor and ground.
3)Start engine and watch O2 sensor output on voltmeter.  A "correct" reading
is a rapid fluctuation above and below .5 volts.  (A graph of the voltage
output vs. air/fuel mixture is roughly "S" shaped with the center of the
"S", corresponding to about .5 volts, being *very* steep.)  A reading
consistently above .5 volts indicates "too rich" and a reading consistently
below .5 volts indicates "too lean."
4)Adjust air bypass on AFM until correct reading is obtained.

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Tom Young                       '81 Vanagon
Lafayette, CA 94549         '82 Westfalia
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