I just fail a smog check in California, my 97 850 has about 300,000 miles on it. It runs great with no check engine light. I did get a code a few moths ago for evap system. Will that effect NO levels? My levels at 15mph where 506 the max is 424, in addition at my last smog two years ago my NO levels where about 200. After decarbonizing it went down to 496. Cat was replaced a few years ago. Any suggestions, should i decarbonize again? Is it bad 02 sensors, one or both, or should I try something else?

sinclairPosts: 1Joined: Yesterday, 13:43

 

What engine (NA, LPT, HPT)? Don't think it does, but does your engine have an EGR valve? If it's clogged that could increase NO.

Inclined to think at that mileage most likely carbon buildup on piston tops; what did you do to de-carbonize?

Have you done a compression test?

Any current DTCs (is your Check Engine Light on)?

 

Glad we don't have inspections. He said it has NO cel.

 

i heard a hiss coming from the fuel pressure regulator, would that have anything to do with this problem.