How good are you at recognizing abnormal O2 sensor beavior

[Bruce Plecan]

-----Original Message-----
From: GRUMPYNOMO at aol.com <GRUMPYNOMO at aol.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Wednesday, September 02, 1998 11:51 PM
Subject: How good are you at recognizing abnormal O2 sensor beavior


>Iam befuddled!

We must be related

 I have a Range Rover with O2 sensors that drift downwards in
>voltage.  Just warmed up the sensors cycle from 800mv to 0mv.  As the
engine
>gets to operating temperature the cycling range drops to 600mv (hi) to
minus
>300mv. (low) with a mean of around 100mv sometimes even below 0!
>
>What's wrong with this picture?

Sounds about right to me.

 What could be causing this?

Normal warm procedure.  Think of it as the choke on, and the
the engine warms up, and leans out..  The ecm hunts for the
perfect mixture, so the O2v floats around.  At WOT, the exhaust
flow is such a large volume, that it appears to be a rather
steady reading.
>
>I have added an extra ground to the sensors and I have changed both of them
>and I have substituted another ecm.
>
>I am going to unplug the alternator and retest.  Please give me the benefit
of
>your opinion if you have a theory or if you have experience in this area
>
>Thanks
>Alan Briggs
>FCECLtd at aol.com
>