Needless to say if the O2 sensor indicates the mix is lean when it clearly is not then the O2 sensor is providing a bad reading. Is it possible the O2 sensor is not coming up to temperature?

Gary

>Can't the O2 sensor be read with it disconnected? Might the readings be different than with it connected? Could the problems be elsewhere?
>
>Gary
>
>Dennis Haynes <dhaynes@OPTONLINE.NET> wrote:
>
>>Just because the O2 sensor is new does not mean it is good. Once they
>>are exposed to excessive carbon or if silicon is used in the wrong place
>>on the engine, it will be toasted. Make sure there are no shorts or bad
>>connections in the wiring and if all appears OK, then get another
>>sensor.
>>
>>Dennis
>>
>>
>>-----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
>>
>
>
>--
>Gary McEachern
>Reading, Ma
>'90 Westy Subavanagon
>'87 Wolfy Subavanagon
>
>
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--
Gary McEachern
Reading, Ma
'90 Westy Subavanagon
'87 Wolfy Subavanagon

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