V12 runs too lean to pass emissions test

1992 JAGUAR XJS
39,000 MILES
Avatar
TONYTIGERFORYOU
  • MEMBER
  • 3 POSTS
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
Oct 13, 2011 at 4:03 PM
Advertisement
Avatar
DOCFIXIT
  • CERTIFIED EXPERT
  • 18,828 POSTS
When NOX high indicates problem with EGR have that checked, cleaned ect
Oct 13, 2011 at 6:10 PM
Avatar
TONYTIGERFORYOU
  • MEMBER
  • 3 POSTS
The car does not have an EGR valve
Oct 13, 2011 at 8:47 PM
Advertisement
Avatar
DOCFIXIT
  • CERTIFIED EXPERT
  • 18,828 POSTS
Who removed it? is car for USA production or imported?
Oct 17, 2011 at 3:16 PM
Avatar
TONYTIGERFORYOU
  • MEMBER
  • 3 POSTS
The car is a USA car. It has a smog pump. Jaguar did not put an EGR valve on it.
Oct 17, 2011 at 4:04 PM
Avatar
DOCFIXIT
  • CERTIFIED EXPERT
  • 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
Image (Click to enlarge)
Attached Media
Oct 17, 2011 at 6:46 PM