[W126 Coupe] Rear End Thumpety-Thump & O2 Sensor Readings

[Lou Carrillo]

For the thumpety, check your center drive shaft bearing.....
  ----- Original Message ----- 
  From: Alexander Hochhausl<mailto:plustech at optonline.net> 
  To: 'Mercedes Coupes Mailing Lists'<mailto:mbcoupes at mbcoupes.com> 
  Sent: Monday, March 03, 2008 5:17 PM
  Subject: [W126 Coupe] Rear End Thumpety-Thump & O2 Sensor Readings


  I have a strange development. Every time I leave a light I get a thumping (pretty much the same, but not relative to speed/duration of acceleration) from the rear. I thought it was exhaust related - like the muffler hitting the body. But I don't see evidence of that - all seems to hang clear. I don't feel it in the drive train (if it were a joint or something) all runs smooth. Does it for 1-2 seconds, then is gone. It's been getting steadily more pronounced. I figure eventually something will fall off - that will solve the mystery. Definitely not tire related - just got new ones.

   

  Second - does anyone know what the "normal" voltage reading for the O2 sensor should be? I can't find it in the service manual I have. I recently noticed a decrease in the normal vacuum while driving - Idle is fine, but driving I need slightly more throttle than normal. I've eliminated vacuum leaks (unless my EGR valve is not shutting) so my suspicion is the O2 sensor is reading "rich" resulting in over compensating on the lean side of the curve. Any thoughts anyone?

   

   

  Thank You,

   

  Alexander Hochhausl, PE

  Tel: 516-909-3794

  '89 560 SEC 

  '81 380 SLC (sold - tears)

     

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