Date:         Sun, 4 Feb 2001 09:53:43 -0600
Reply-To:     Larry Alofs <lalofs@ENTERACT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Larry Alofs <lalofs@ENTERACT.COM>
Subject:      Re: O2 Sensor Voltage
Comments: To: David Beierl <dbeierl@ATTGLOBAL.NET>
Content-Type: text/plain; charset=us-ascii

> At 06:44 PM 2/3/2001, Mark Keller wrote:
> >.8 volt or higher, weak vane
> >spring setting, malfunctioning fuel pressure regulator too high system
> >pressure, Or too lean .3 volts malfunction of fuel pressure to low or a
> >poorly adjusted afm wiper.
>
> Voltage = oxygen present = too lean.  IOW this is backwards.  I still
> question whether having an open-loop reading that's not in the middle of
> the range is reason to begin fiddling in the absence of other indications
> (smells rich, poor mileage, Rome burning... I dunno).
>
> david
>

David,
  I think Mark's right on this point.

According to the Bosch F.I. manual sold by Bentley (pp. 21-23):

 The O2 sensor generates a voltage directly related to the *difference* in O2
content between the ambient(outside) air and the exhaust stream.
 Lean -> more O2 in exhaust -> less voltage produced.

I was forced to learn a little about this when my previous vanagon ('84) failed
the IL emissions test.  Turned out there was a crack on the underside of one of
the hoses connected to the intake.  Watch out for those vacuum leaks!

Larry A.
Chicago
91 GL