Steve,
I just looked at my Bentley and on the 8V Digifant II and
both 16V Motronic wiring diagrams there is a wire that comes off of
the O2 sensor wiring after the plug and is bare copper. This, at
least on my 8V 92 appears to be wrapped around one of the sensor
wires and acts as a drain. In the diagram on page 245, current track
26 is what I am talking about. Look at the diagram and you will see
that there is a circle drawn just under the #7 Motronic terminal and
off that, to the right and down, comes the wire I am talking about.
Even though it is identified as Black, it is bare copper. My son's
92 8V had a crap running condition similar to yours and required not
only a new O2 sensor but when we were tie-wrapping everything back in
place, we spotted that the bare wire had broken. As a precaution on
my car, I extended it to the back corner of the cylinder head and
neither of us have had a problem since. With engine mounts wearing
out, the fore and aft motion of the engine sometimes puts extra
strain on any of the cables running between the bulkhead and a
grounding point on the engine. In my last Motronic car I extended
all the brown leads I found in that area with some wire mesh similar
to the grounding strap that runs from the back corner of the hood to
the fender on the driver's side and had no problems. I'd say it is
worth a try......Jack
when I unplug it nothing happens, if I ground it, the current goes to
+-20mA, which the Bentley says means the ECU is OK.
I swapped the DPR, Knock box, airbox, ECU and lastly the O2 sensor
w/spares I have and no change.
I imagine the O2 sensor needs a ground. Has anyone ever heard of
grounding problems with the O2 sensor?
I'll pull the sensor and check my soldering....
the O2 sensor wire is shielded. I remember something in the Bentley
about where the shield is grounded but can't find it now. Could a bad
shield have anything to do with it?
thanks again,
Steve
