O2 sensor voltage output

[Orin Eman]

> Hello all:   I have been tuning my Vette for a while using a tech1 for
> snapshot and trying to get the 02 sensor to at least 800mv at wot.   I have
> the MT program for my 87 Vette and I keep adding fuel trying to get the 02
> sensor voltage higher up.  Lately it seems to want to go leaner.  700mv
> range.  It isn't detonating,  I pulled timing out to try and eliminate that
> too.  I'm running a total of 31 deg now,  stock prom is 36 deg total.  Could
> the 02 sensor be contaminated with high temp silicone from the exh gaskets?
> Do these things just get tired?  It still has the stock exh system so the
> location of the 02 sensor hasn't changed.   Any suggestions/answers?

How are you measuring the O2 voltage?  What are you using as a ground
reference?  For a 1 or 3 wire sensor, the ground reference for the
sensor is the manifold it is mounted in.  There can easily be
0.1 to 0.2 V difference between the manifold and other grounds
in the car...  So if you aren't using the manifold as your reference,
you may well never get over 700mV.

It is also possible that it got poisoned, but a new sensor would
be an easy check.

Orin.