Thanks Mark I will definitely check that wire.

David Clarkson

-----Original Message-----
From: mark drillock <mdrillock@cox.net>
To: David Clarkson <dvdclarksn@AOL.COM>
Cc: vanagon <vanagon@GERRY.VANAGON.COM>
Sent: Fri, Dec 28, 2012 11:13 am
Subject: Re: O2 sensor type problem after replacing O2 sensor

The O2 heater is powered by the FP relay in 1990 so it should be 
heating
whenever the engine is running.

The ECU watches the Temp2 sensor and ignores the O2 reading unless the
Temp2 shows the engine coolant temp to have reached a warm enough 
level.
A bad or intermittent connection to the Temp2 could cause the ECU to 
run
in cold mode and I believe that will be a rich condition. Not rich
enough to kill the engine though.

The ECU uses a special ground to compare the O2 reading to and if that
special ground is weak or missing then it will get false readings from
the O2 sensor.

The special ground is the brown wire that comes out of the small bundle
going to the distributor hall connector. The brown wire has nothing to
do with the distributor. Make sure the brown wire has a good ring
terminal crimped on to it and is bolted down to clean metal on the 
engine.

Mark