I have a 1997 Honda Civic EX, automatic, with 238k in california. I went for a smogcheck last week and my results were:

Speed=15Mph
RPM=2040
%CO2=14.9
%O2=0.0
HC(PPM) Max=66 AVE=9 MEAS=66
CO(%) Max=0.57 AVE=0.03 MEAS=0.29
NO(PPM) Max=487 AVE=67 MEAS=822
"FAIL"


Speed=25Mph
RPM=2007
%CO2=14.9
%O2=0.0
HC(PPM) Max=49 AVE=6 MEAS=49
CO(%) Max=0.55 AVE=0.03 MEAS=0.25
NO(PPM) Max=774 AVE=62 MEAS=702
"PASS"

My mechanic is telling me it will be difficult to pass it but there was no clear explain what my options are, things like what he can replace. hoping if anybody could suggest what i can do.. thank you.

 

If it's a California model with EGR, clean the EGR valve and the EGR passages in the intake manifold. You need to take off the fuel rail then unbolt the plate on the top of the manifold and scrape out the carbon which is undoubtably there.

After that, high levels of all 3 pollutants usually means the catalytic converter is bad.

 

thanks for your advice mk378.

checked my smog test result sheet and technician did not find EGR in my car which means my car happend to be not california model.

i changed catalytic converter a couple of years ago at 200k miles if changing it reduce all 3 pollutant number i will do it. i will talk to my mechanic again in this week.

thanks.

 

Make sure the ignition timing is set to spec and that the engine is not running hot.

 

so i brought my car, they inspect our car.

they found crack at mani-fold. i was hearing noise from engine thought engine went bad but fortunately it was just mani-fold. They recommended to change it first with O2 sensor. replacing those 2 items + inspection fee was $659.

after changing mani fold + co2 sensor, number went down to
HC:35
CO:0.1
NO:600 (not pass)

NO did not pass. they now recommend to change catalytic converter. i am planning to do so, i guess. any other idea in order to dropp NO measure?