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Date:         Tue, 13 Jul 2004 17:44:31 -0500
Reply-To:     Aerowolf <aerowolf@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Aerowolf <aerowolf@GMAIL.COM>
Subject:      Re: Running rich, O2 sensor says lean, exhaust leak?
In-Reply-To:  <b3a1e7ad0407131415580ea66@mail.gmail.com>
Content-Type: text/plain; charset=US-ASCII

It's an electrical system (i.e., voltage runs from ground to the O2 sensor to the ECU to the positive terminal). If the ground connection is bad, the voltage is going to be less than it needs to be for the ECU to properly interpret, thus it's going to have problems.

The ground is /VITAL/. On /all/ electrical systems.

-Kyle

On Tue, 13 Jul 2004 14:15:58 -0700, Craig Oda <craigoda@gmail.com> wrote: > Laurence, > thanks for the tip. This might be a source of problems. I do notice > that the ground wire is slightly corroded and worn out a bit. I > dropped the current engine in about a year and a half ago. At the > time, I cleaned the contacts. Maybe I need to do it again with a > fresh fat battery cable in there. > > You think this is the primary ground I should clean first? I cleaned > the big fat one under the van about 2 years ago. > > The thing that I don't understand is why the O2 sensor keeps telling > me (and the van's computer) that the exhaust is lean. Could this be > caused by a bad ground to the engine block? > > I'm using a single wire O2 sensor. So, it's grounded to the exhaust > system. I was thinking about running a ground from the sensor to the > engine block. You think this would help? > > Regards, > Craig > > > > > On Tue, 13 Jul 2004 14:08:34 -0400, Laurence Smith > <laurence@alanasmith.com> wrote: > > 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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