Date: Tue, 13 Jul 2004 22:30:18 -0400
Reply-To: ROBERT DONALDS <donalds1@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: ROBERT DONALDS <donalds1@VERIZON.NET>
Subject: Re: Running rich, O2 sensor says lean, exhaust leak?
Content-Type: text/plain; charset="iso-8859-1"
Craig
once the exhaust is sooted up you need disconnect the oxy sensor and drive
the van or it just fouls out one sensor o2 after another. You said the van
runs fine without the sensor connected. So with this thought in mind you
dont need the o2 sensor to drive the van. give the exhaust a chance to clear
out say 200 miles and reconnect the o2 sensor
in the mean time change the oil its full of fuel and keep a close eye on the
milage if it does not go way up you still have a problem.
let me know
Bob Donalds
Boston Engine
----- Original Message -----
From: "Craig Oda" <craigoda@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, July 13, 2004 1:38 PM
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
>
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