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