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
>