I have a 92 civic dx with a D16z6 swap... it is stock out of a 93 si. i failed e-check twice due to my NO levels were to high... first time i had no cat. so i put one on and still fail. i can no longer get 30 day tags so i must resolve this matter VERY SOON. some one sujested it was my EGR valve ..... but ihave no clue where it is. My engine light is on but when i check for codes it doesn't blink.... it just stays on (i have a p28 ecu) any help would be great.

 

There is no EGR.

NOx can be caused by a lot of things. You could be running lean, your ignition timing may be too far advanced, you may have carbon build up, your fuel injectors may be clogged, your fpr may be bad, your fuel filter may be clogged, your cat or O2 sensor could be bad.

 

^^^ what he said... plus
if your CEL is on you will not pass emissions anyway.
also if your ECU is in limp home mode due to the CEL it's running rich and ignition retarded.

is the P28 chipped?