What the O2 sensor does is provide feedback to the ECU as to the fuel/air ratio so the ECU can compensate for a basic too-rich/too-lean condition.  *IF* everything is set properly on your engine then you *don't* need the O2 sensor to run; after all if everything's OK then just having the O2 sensor tell the ECU "air/fuel mixture is correct" doesn't add anything. 

You don't say what you were doing with the O2 sensor wire so I can only guess you've shorted out the middle "signal" wire to the coax sleeve that surrounds it.
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Tom Young                       '81 Vanagon
Lafayette, CA 94549         '82 Westfalia
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  ----- Original Message ----- 
  From: Jason Willenbrock 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Thursday, January 15, 2004 4:42 PM
  Subject: O2 problems

  these pesky lil' things!
  Okay on my 90 gl i was screwing around with the O2 sensor wire, don't ask why.  anyways now with the O2 connected the vans runs supper rich with black smoke and finally sputters then dies.  i disconnect the O2 runs great, bit of a high idle though around 1000, but otherwise fine.  reconnect the wires, runs bad again.  seems to me like a ground thing.  if i disconnect the green wire but not the snap wire, it runs fine.  if i disconnect the snap wire but connect green wire, it runs bad again.  what is up?  where does the ground for the O2 go so i can clean it up.  why does it run fine without O2, and can i just run it without O2 connected?  what does this thing really do except cause problems?