Date: Tue, 13 Jul 2004 17:58:00 -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: <b3a1e7ad04071310383594a82f@mail.gmail.com>
Content-type: text/plain; charset=us-ascii
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
