Date: Tue, 13 Jul 2004 18:28:29 -0400
Reply-To: Gary McEachern <GlmceN@NETSCAPE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Gary McEachern <GlmceN@NETSCAPE.NET>
Subject: Re: Running rich, O2 sensor says lean, exhaust leak?
Content-Type: text/plain; charset=iso-8859-1
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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