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Date:         Thu, 8 Jul 2004 09:03:25 -0700
Reply-To:     Craig Oda <craigoda@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Craig Oda <craigoda@GMAIL.COM>
Subject:      fuel/air mixture diagnostics
Content-Type: text/plain; charset=US-ASCII

I have some problems getting my automatic transmission van to consistently idle when stopped at a light, especially if the idle is set at 900rpm. I need to set it higher.

I have a voltmeter attached to my oxygen sensor and it is indicating a very lean mixture. I have the air-fuel screw on the AFM almost all the way in (clockwise). When I get home tonight I'm going to try and move the ratchet wheel inside the AFM that controls spring tension. Then, adjust the air-fuel mixture screw again.

I'm new to these diagnostics. For a while, I assumed that my van was running rich because there is black soot on the tip of the exhaust pipe. Does black soot on the exhaust indicate a rich or lean engine? Or, is it possible that the soot could be an indication of either condition? It seems to me that I can smell unburnt gas from the exhaust. However, this could just be my imagination?

The O2 sensor reading indicates the engine is lean. The soot makes me wonder.

Before I fiddle with the AFM, I thought I would ask the friendly vanagon people.

Other info: - O2 sensor is less than 6 months old - new fuel filter, air filter, fuel pump - new spark plugs, plug wires, rotor, distributor cap

Also, I have a vacuum guage from Sears that I never used. I may tap it into my vacuum hose system tonight for a test. Where Should I connect it? I can't detect any vacuum leaks with ear or carb cleaner.


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