Hey Now,
My roomate 93 honda civic lx 4cyl. Last year it barely passed Atlanta Georgia emissions. This year he just passed his NOx but his HC ppm and his CO% was thru the roof. I helped him change his cat now the HC and CO passes fine, but his NOx went up and is now failing that. NOx I thought was controled by the EGR valve but this car doesn't seem to have one? The car runs great no knocks, pings, nada. There is a stored massege we viewed with my co-workers snap-on scanning tool. It states over lean condition and possible fault fuel pressure regulator. A shop repair guy thinks it's the map as it has more control over fuel mixture. The scanner check the O2 sensor was ok, as it was replaced some time back. i don't hear any obvious vacume leaks. Can some help me please !
John