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V12 runs too lean to pass emissions test

Tiny
TONYTIGERFORYOU
  • MEMBER
  • 1992 JAGUAR XJS
  • 39,000 MILES
Always has trouble with NOX too high. Have tried multiple de-carbonizing additives in the fuel. Brand new O2 sensors, brand new complete exhaust system including cats, new spark plugs, fresh oil, new ignition coils. From what I have read this was the first year for the HE heads, designed to run more on the lean side to improve mileage and pass California emissions laws, since California is a big market for these cars. There must be some component or trick to make this car run a little richer.
Any info on this?
Thanks,
Tony
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Thursday, October 13th, 2011 AT 4:03 PM

5 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
When NOX high indicates problem with EGR have that checked, cleaned ect
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Thursday, October 13th, 2011 AT 6:10 PM
Tiny
TONYTIGERFORYOU
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  • 3 POSTS
The car does not have an EGR valve
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Thursday, October 13th, 2011 AT 8:47 PM
Tiny
DOCFIXIT
  • MECHANIC
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Who removed it? Is car for USA production or imported?
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Monday, October 17th, 2011 AT 3:16 PM
Tiny
TONYTIGERFORYOU
  • MEMBER
  • 3 POSTS
The car is a USA car. It has a smog pump. Jaguar did not put an EGR valve on it.
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Monday, October 17th, 2011 AT 4:04 PM
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Right XJ6 has EGR the XJS uses air pump and 4 cats. Maybe air pump diverter valve faulty pump only adds air to exhaust under warmup if adds air when O2 are operating CATS will run hot causing NOx
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Monday, October 17th, 2011 AT 6:46 PM

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