Date:         Mon, 4 Mar 2002 10:20:27 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Voltages from O2 sensor
Comments: To: WVVW <wvveedub@NETSCAPE.NET>
In-Reply-To:  <2B812878.5CC17502.00B0D2D4@netscape.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 07:34 AM 3/4/2002, WVVW wrote:
>1)leave the O2 sensor connected and take the reading from the O2 lead to
>ground?

This will show you whether the ECU is running in closed-loop mode or
not.  Steady reading ~ half a volt indicates not sensor not hot enough to
work yet; random-looking readings above and below half a volt indicate
proper closed-loop operation.   An oscilloscope would show a sort of crappy
square wave as the ECU drives the mix back and forth across the
stoichiometric point.


>2) Disconnect the O2 sensor and take the readings from the disconnected leads?

This will put the ECU in open-loop mode and show you whether the mix is
rich or lean under the given conditions.  Voltage near 1 volt is rich; near
0 is lean.  It's extremely sensitive though, can't tell how rich or how
lean beyond a uselessly tiny range.  The ECU in closed-loop doesn't even
try; it just hunts back and forth across the line.

You have to use a meter with at least 10 megohms input impedance to keep
from loading down the line and getting false-low readings.

>3) When doing the CO2 adjustment, should the idle stabilizer be connected
>or bypassed?

CO?  I'm too lazy to look it up in Bentley, but bypassed is probably
specified and is certainly OK.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"