This seems normal.  You can disconnect the O2 sensor wire and see if
your van drives any better.

Symptoms I had:
  - black soot in exhaust from engine running rich
  - lack of power
  - O2 sensor voltage hovering below .1 volts while the van was in use

Sensor looked black and sooty.

My understanding is that the sensor is supposed to fluctuate between
0.2 volts and 0.8 volts, with 0.45 being optimal.  Normal operation is
for the voltage to constantly be going up and down around the "normal"
optimal air/fuel mixture.  I think that it's also common to run the
engine a bit rich, maybe around 0.6v since performance degrades faster
when the engine is lean rather than rich.

The only reason I solved my problem and got to know a little bit about
the O2 sensor is because of the nice people on this list.

-- Craig

On Wed, 14 Jul 2004 10:49:08 -0400, Eric Zeno <vw4x4@fyi.net> wrote:
> I have a inline 4 cly. in one of my
> Syncro's, with the CIS-E fuel system on
> it.  Anyone know what symtoms a bad O2
> sensor in this system would cause?  I
> put an digital volt measer on the O2 sensor
> and the readings were jumping rapidly from
> .2volts to .6volts.... ??
>                        Eric
>