Laurence,
thanks for the tip.  This might be a source of problems.  I do notice
that the ground wire is slightly corroded and worn out a bit.  I
dropped the current engine in about a year and a half ago.  At the
time, I cleaned the contacts.  Maybe I need to do it again with a
fresh fat battery cable in there.

You think this is the primary ground I should clean first?  I cleaned
the big fat one under the van about 2 years ago.

The thing that I don't understand is why the O2 sensor keeps telling
me (and the van's computer) that the exhaust is lean.  Could this be
caused by a bad ground to the engine block?

I'm using a single wire O2 sensor.  So, it's grounded to the exhaust
system.  I was thinking about running a ground from the sensor to the
engine block.  You think this would help?

Regards,
Craig

On Tue, 13 Jul 2004 14:08:34 -0400, Laurence Smith
<laurence@alanasmith.com> wrote:
> You did not mention cleaning the grounds, especially the one on the
> engine, driver's side head.  If this ground is bad you get very rich
> symptoms.
>
> ----------------------------------------
>  Laurence Smith
>  Hamilton, Ontario, Canada
>  90 Westy / 90 Subie 2.2
>  87 GL / 91 Subie 2.2
> ----------------------------------------
>
>
>
>
> > -----Original Message-----
> > From: Vanagon Mailing List
> > [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> > Of Craig Oda
> > Sent: Tuesday, July 13, 2004 1:38 PM
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: Running rich, O2 sensor says lean, exhaust leak?
> >
> >
> > This past weekend I averaged 5 mpg and there was a lot of unburned
> > fuel coming out of the exhaust.  I've got a voltmeter
> > hooked up to the
> > O2 sensor and the voltage was measuring consistently lean,
> > despite the
> > obvious signs of the engine running rich, such as gas smell
> > and black
> > smoke, not to mention high fuel consumption.  There  was also
> > drivability problems, including loss of power and some surging.
> >
> > This morning I disconnected the O2 sensor before I went to
> > work.  The
> > engine drove much better.  I'm now thinking that there is an exhaust
> > leak that is causing air to leak into the system and causing the O2
> > sensor to read the air-fuel mixture incorrectly.  Although
> > this seems
> > counter-intuitive since the exhaust is presumably under pressure in
> > the system and pushing out of the back, I've heard of a
> > process called
> > exhaust scavenging where an exhaust pulse pulls exhaust through the
> > system.  Each high pressure exhaust pulse travelling through the
> > system results in a bit of pull
> >
> > I obviously want to reconnect my O2 sensor.  Before I take off the
> > exhaust system and change the exhaust gaskets, is there
> > anything else
> > I can check?
> >
> > Stuff I've done in the past week:
> >   - changed O2 sensor
> >   - changed fuel pressure regulator, fuel pump, fuel filter
> >   - took apart entire air intake system, changed the air intake
> > distributor box, and most rubber hoses.
> >    - changed temp sensor II
> >    - adjusted valves
> >    - looked for exhaust leaks under the van, but couldn't find any
> > obvious ones.  I haven't taken the system off for
> > inspection.... yet.
> >
> > Also, my exhaust system has a dent in it right after the O2 sensor.
> > Could this be causing a problem with the exhaust flow?
> >
> > I have a spare exhaust system and a newish auxiliary air regulator
> > that I can swap in for a test.  Right now, I think it is air leaks
> > into the system or maybe that dent.
> >
> > Any advice before I crawl around under the van and get dirt
> > falling in
> > my face, hair and eyes?
> >
> > -- Craig
> >
>
>