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What's the point in replacing rear (downstream) o2 sensors?

  • Thread starter Thread starter poindexternasty
  • Start date Start date Nov 17, 2008
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poindexternasty

New Member
Apr 29, 2008
148
0
0
Nov 17, 2008
#1
  • Nov 17, 2008
  • #1
hey all,

as the title asks, what is the point or purpose in replacing the downstream oxygen sensors on a stock 02 GT w/ 101k miles? I replaced my *up*stream sensors a few days ago to fix a low-rpm stumble, miss, and hesitation. The car runs great now but I am wondering if I should have replaced the downstream ones as well.

It is my understanding that the downstream sensors measure catalytic efficiency. If my cats are working properly (not smelling sulfur or gasoline in exhaust), should I still swap them out? Do they serve a real purpose that relates to performance, efficiency, environmental issues?
 

SaleenGT2001

Well-Known Member
Jul 18, 2005
2,811
4
58
Four Oaks NC
Nov 17, 2008
#2
  • Nov 17, 2008
  • #2
their entire purpose is to make sure your cats are working. most people just eliminate them with a tuner.
 

AdRock

Member
Nov 13, 2003
521
1
19
South Texas
Nov 17, 2008
#3
  • Nov 17, 2008
  • #3
If you don't hacve a CEL telling you that their is a problem with them then don't worry about it it.
 

Rusty67

20+ Year Stangneter
Dec 3, 2002
3,749
37
109
LA, CA
Nov 17, 2008
#4
  • Nov 17, 2008
  • #4
AdRock said:
If you don't hacve a CEL telling you that their is a problem with them then don't worry about it it.
Click to expand...

If you do throw a CEL/MIL I wouldn't replace them. An MIL eliminator is cheaper then a new O2 sensor.
 
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