When you say you're getting those readings on the "O2 sensor with it hooked
up to the ECU" I assume you mean the voltmeter is "inline" between the O2
sensor and the ECU?  If so, re-run your test with the O2 sensor
disconnected.  The O2 sensor should put out a voltage of right around .5
volts at the correct air/fuel mixture (the graph of voltage vs. mixture is
*very* steep right around the "ideal" mixture, so you should see a rapid
fluctuation above and below .5 volts) with higher voltage indicating "too
rich" and lower voltage indicating "too lean."  What you're reading is the
output of the O2 sensor, the ECU's attempts to correct, and whatever
distortion you're introducing with the voltmeter.

Doing the test with the O2 sensor disconnected will give you an indication
of the basic mixture before the ECU tries to correct it.

You adjust the air/fuel mixture after making sure that every other aspect of
the engine - mechanical, ignition, vacuum, etc. - is correct.  Adjustment of
the air/fuel mixture screw is the first thing to try to correct a "too rich"
situation
---------------------------------------------------------------
Tom Young                       '81 Vanagon
Lafayette, CA 94549         '82 Westfalia
---------------------------------------------------------------
----- Original Message -----
From: "Chad Morris" <chad@ALLMORRIS.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, September 11, 2003 10:20 AM
Subject: O2 readings

I am reading between .81 and .89 volts on my O2 sensor with it hooked up to
the ECU.  I am thinking that indicates I am running rich.  Assuming my O2
sensor is good, what would the ideal reading be?  If it is indeed running
rich, should I be able to remedy that simply by turning the air/fuel mixture
screw, or will I need to mess with something else to get it to run right?
Any thoughts?