Just failed a CA smog cert. Attached is the readings from the test. the guy who did the test said replace the O2 sensor and the catalytic converter...what do the experts suggest??

 

Those measured values look like either an instrument error has occurred or your engine wasn't at full warm operation. The difference in RPMs is only 56 and yet the difference in NO is 279. A huge difference like that over such a small variation in RPMs indicates that it was running rich in the same manner as a cold engine.

Was everything at full warm operating condition for test conduct? How much time is allowed before retest is required?

I think you can clear that up without replacing components but it will take anywhere from a few days to a couple weeks for fuel system and air/fuel induction cleaning to cause an appreciable change in those measured values. One simple solution is to add Marvel Mystery Oil to your fuel at a mix ratio of 4 oz. of the oil per 10 gal. fuel. Drive through a tankful, get some WOT highway speed runs into it to blow out the carbon deposits, and then do it again before repeating the emissions test. Those measurement numbers will be reduced to near average values and you won't have replaced any components. Just be careful to not get any speeding tickets in the process...

 

I had the exact same problem, it's not a sensor or the cat....



Through an insane amount of research I found that excessive combustion temps cause the dreaded high NOX.

I installed colder plugs and passed with flying colors

 

I had that problem, but my no.1 rings where burnt so I was just killing my spark plug lol

 

i had been running around town, so i think i was definetly at running temp. i will do both....spark plugs and mystery oil and retest and see what happens. i will keep you updated...thank you.

i love this forum

 

It ended up being a bad cat. I qualified for the CAP program and paid about 120 for 600 worth of work.