How to get a 94 mazda protege to pass smog?

I have a mint condition 94 Mazda protege that has high nox #'s but no EGR valve to change Could it be the Cat converter?|||It could be. The first (cheaper) alternative is a coolant flush. That will bring the engine temperature down; NOx is caused by high temperatures and pressures fusing nitrogen in the air with oxygen. My NOx readings went from 1700 to below 100 after a very thorough coolant flush.





The more expensive solution (if flush fails) will be to replace the 3-way catalytic converter. The rhodium catalyst (the one that converts NOx back to N2 and O2) is the first catalyst to get clogged with engine soot.