Hello everyone, we'll I failed smog again if any one can lead me to the right direction would be much greatful. I have a 1999 honda accord 3.0 vtech 197,000 miles runs really good

first readings: Took car not very warm

15 mph 1725 rpm co2 (%) meas 14.6 02(%) meas 0.18 HC(ppm)meas 30
CO(%) meas 0.01 NOx (PPM) 688 I failed NOx
25 mph 1664 rpm co2 14.54/o2 0.06/HC 20/ COo.25 / NOx 238 passed

As you can see I failed only at 15 mph with NOx being higher than max

what I did after first attempt

1. changed oil,spark plugs,cleaned egr valve and used seafoam to clean injectors put the rest in the tank.
2. I drove car for a week and tried testing again with engine warm this time.
3. I still failed Nox at 15 mph and looks like I barely passed HC
4. second readings 15 mph CO2 0.17--HC 54 max 54-- CO 0.00--failed Nox 499 max 430 closer
25 mph CO2 14.6 -- HC meas 35 max 37 close--CO 0.00-- NOx meas 538 max 717 close but this time it was higher than first attempt. over all 25mph passed

 

High Nox readings are usually result of a worn out or faulty catalytic converter or EGR system.

 

Was the EGR passage cleaned too? Requires intake manifold removal:

www(dot)youtube(dot)com/watch?v=HRp6RWZ1egM