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Date:         Tue, 13 Jul 2004 14:08:34 -0400
Reply-To:     Laurence Smith <laurence@ALANASMITH.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Laurence Smith <laurence@ALANASMITH.COM>
Subject:      Re: Running rich, O2 sensor says lean, exhaust leak?
Comments: To: Craig Oda <craigoda@GMAIL.COM>
In-Reply-To:  <b3a1e7ad04071310383594a82f@mail.gmail.com>
Content-Type: text/plain; charset="US-ASCII"

You did not mention cleaning the grounds, especially the one on the engine, driver's side head. If this ground is bad you get very rich symptoms.

---------------------------------------- Laurence Smith Hamilton, Ontario, Canada 90 Westy / 90 Subie 2.2 87 GL / 91 Subie 2.2 ----------------------------------------

> -----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 >


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