The root of your problem may or may not have anything to do with the O2
sensor.  Regardless, you should check its operation with a voltmeter.  When
the engine is well warmed up, watch the voltage on the signal wire while
idling and at 2000 rpm or so.  Be sure the negative lead from your meter is
hooked to a good ground.  If the sensor is connected to the ECU and things
are working, the voltage should move up and down from a tenth of a volt or
so to eight tenths or more.  This should happen more rapidly at higher RPMs.
  If the voltage stays high, the exhaust contains unburned fuel (too
rich).  If the voltage stays low, either the sensor doesn't work, or the
mixture is too lean.  What to do with this information can still be a
problem, but more info is always a starting point.

Fuel injector problem are one strong possibility when rough running and
mixture problems occur.  Others will probably give you more pointers.

The should be a little shield around the O2 sensor where the wires emerge
to protect that area from water, mud, and snow, etc.  If yours is missing
you should improvise something.

Good luck,
Larry A.

On Wed, Jan 6, 2016 at 5:05 PM, Richard Golen <rgolen@hotmail.com> wrote:

> Good Afternoon,
>
>
> In 11 days, I'm leaving for a road trip to the Keys with my 87 Westy. In
> preparation, I've been doing various repairs, etc. One of the things I did
> was to put in a new O2 sensor. The previous one had its wires cut by the
> "mechanic" who worked on it a couple of years ago. Periodically, when the
> previous O2 sensor got wet, the engine would loose power, wouldn't idle and
> ran rich. I could cure it by shutting off the ignition and turn it back on
> quickly. It would clear the problem for a while. Eventually I disconnected
> the wires to the sensor.
>
>
> Yesterday, the new 02 was installed and connected, and within 5 minutes,
> the old symptoms (loss of power, etc) returned. Turned off the ignition and
> turned it back on, and it cleared the problem for a couple of minutes.
> Drove home and then disconnected the wires to the O2 sensor. Took the van
> for a drive. Ran like a champ for about 5 minutes, and the loss of power,
> rich running, etc. started up again. This is the first time its run this
> way with the O2 sensor disconnected.
>
>
> When it "idles" its runs roughly at 300 rpm and puffs out black smoke.
> I've blown through 1/2 a tank in 80 miles.
>
>
> HELP? Any ideas?
>
>
> Thanks,
>
>
> Ric
>