Date: Tue, 13 Jul 2004 23:01:51 -0400
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: Running rich, O2 sensor says lean, exhaust leak?
In-Reply-To: <41AB90C6.21E4656F.0004AB8A@netscape.net>
Content-type: text/plain; charset=us-ascii
Yes it can.
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Gary McEachern
Sent: Tuesday, July 13, 2004 6:15 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Running rich, O2 sensor says lean, exhaust leak?
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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