After my previouse wan problems this is what happened today!!
 
Today is was DRY so I tried an experiment.  Several times on the way home I unplugged and replugged the 02 sensor in and out  Id it like every 5-10 minutes.  With 02 sensor slight bucking every once in a while.  Without, the idle kicked up a little, bucking gone, but acceleration slightly slower.  (Previoius with 02 sensor connectd i was getting 19-20mpg)  Then comes the weird thing.  A few minutes after the last time I replugged the sensor, horrible bucking, whuite smoke out exhasut, then black smoke.  Shut off, disconnected 02 sensor.  Van restarted, ran fine.  ANy Ideas??

Matt 89 GL Westy