Date:         Wed, 30 Aug 2006 19:37:51 -0700
Reply-To:     Mark Drillock <mdrillock@COX.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mark Drillock <mdrillock@COX.NET>
Subject:      Re: Did the mechanic do something?
In-Reply-To:  <44F5ED18.4090109@verizon.net>
Content-Type: text/plain; charset=us-ascii; format=flowed

While there may be good reasons for checking the effect of disconnecting
the oxygen sensor, the fact that an engine runs better with it unplugged
in no way proves that anything is wrong with it or it's wiring.

The oxygen sensor provides an exhaust gas feedback signal to the ECU but
it can only see the combined gases of all 4 cylinders put together. If
one cylinder is putting out a much different oxygen level than the other
3, this throws the combined reading off and the oxygen sensor signals
this off reading to the ECU. The ECU may then attempt to correct this
combined reading but can only do so by adjusting all 4 cylinders at
once, even the 3 that were in fact working fine. This can result in an
overall worse running engine than would be seen with a disconnected
oxygen sensor in spite of the fact that the oxygen sensor was doing it's
job properly.

Mark


Sam Walters wrote:

> Charles,
>
> Attached are some files for assistance in diagnosis of fuel injection
> system difficulties.
>
> Disconnect the O2 sensor and see if the problem goes away.  If so, it is
> either the O2 sensor or its wiring.  You can run this way for a day or
> two to compare.  Wiggling the wire is no test of the O2 sensor.
> ........................
>
>