Date:         Thu, 4 Nov 1999 14:48:02 -0500
Reply-To:     karl <thewestyman@MINDSPRING.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         karl <thewestyman@MINDSPRING.COM>
Subject:      Re: Oxygen sensor: is a shielded wire necessary?
Content-Type: text/plain; charset="iso-8859-1"

Here's the update on this. Several knowledgeable folks on the list explained
to me the importance of the shielding (thank you all!), so I bought a piece
of shielded wire from the local Radio Shack, and set out to do the fix.
Routed the wire through the floor beneath the ECU, (this seemed the easiest
way to get the wire to the outside, considering it is a Syncro). I then
slipped a short piece of rubber tubing in the hole to insulate the wire from
the metal. Then routed the wire along with the other wiring near the fuel
pump, and back to the oxygen sensor. All done.......except maybe I should
clip the old wire away so that it doesn't confuse someone........what's
under the electrical tape on the old end?.........THE PROBLEM: The previous
mechanic (or the owner?) had replaced the wire end, and thoughtlessly
wrapped the shielding with the signal wire, effectively shorting it out.
What a simple solution, of course it never occurred to me that someone would
do something like that! Oh well, it has a new wire now!

Karl M


----- Original Message -----
From: karl <thewestyman@mindspring.com>
To: Vanagon List <vanagon@gerry.vanagon.com>
Sent: Wednesday, November 03, 1999 8:12 PM
Subject: Oxygen sensor: is a shielded wire necessary?


> Today I diagnosed a Vanagon problem I had never seen before. The customers
> van would start and run fine when cold, but gradually begin to run more
and
> more rich (i.e. black smoke) as the engine temperature increased, and
become
> undriveable. After much swapping and testing of sensors, AFM's, ECU's, I
> found the problem to be a shorted out oxygen sensor lead. This being the
> large bright greeen wire from the ECU, through the harness, and to the
> oxygen sensor. The shielded portion of the lead is shorted out to the core
> of the wire, effectively shorting the entire OXS lead. I clipped the
> connection to the shielding, near the ECU plug (actually, inside the
plug),
> and the problem is totally gone! NOW, the question: What is the actual
> purpose of the wire shielding, and will it be OK to leave it disconnected?
> Does the shielding prevent electrical signal interference? The other
option
> is to replace the complete shielded wire, which could be a huge hassle
given
> that this is a Syncro. Any experts out there care to take a stab at this?
> Thanks!
>
> Karl M
>