Help: My 1990 Integra didn's pass SMOG NOx
 

Hi, New here so thanks for any advice in advance.

I just moved back to Cali and need to register my '90 Integra here again. I just had it smogged and it failed the Nox.

%CO2 %O2 HC (PPM) CO (%) NO (PPM)
Test RPM Meas Meas Max Ave Meas Max Ave Meas Max Ave Meas
15mph 1942 14.8 0.1 121 31 87 .76 .10 .43 807 237 902
25mph 2086 14.8 0.0 96 20 67 .65 .09 .47 746 199 621

before going in i changed the plugs and had the fuel system cleaned.

after going in i changed the oil.

Should I replace the Cat? What else should I do before taking it back in?

thanks again, sanjay

Have a top end cleaning performed, it will blow all the carbon and crap out of the tail pipe and make for good combustion. If that does not work, and you are not throwing any codes, then it may be time for a new cat.

Buy good gas too. Chevron is the best. It burns cleaner. Alot of petroleum companies are adding %10 methonal. It might sound cleaner but it burns faster, gives u less performance and if they're going thru all that trouble to make money chances r they r buying the cheapest gas to begin with.