Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (July 2004, week 2)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Tue, 13 Jul 2004 10:38:14 -0700
Reply-To:     Craig Oda <craigoda@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Craig Oda <craigoda@GMAIL.COM>
Subject:      Running rich, O2 sensor says lean, exhaust leak?
Content-Type: text/plain; charset=US-ASCII

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


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.