O2 sensors and white smoke

[Todd King]

  Hard and fast rule: black smoke is from a rich mixture, blue smoke is oil, 
  white "smoke" is water (steam). Has your engine overheated recently? The first 
  thing to do is very carefully determine the color of the smoke; it may be 
  light blue. Does it behave like a real cloud of smoke (ie dissipated only by 
  the wind) or does it wisp away quickly like steam before any wind would have 
  dissipated it? Hope this helps.
  
  Todd  Todd_King at ccm.co.intel.com