car did not pass emissions, NEED HELP!

[blacknightteg]

alright so first off i want everyone to keep in mind that my car is running a b20 with an ls ecu and its chipped and tuned.

well i took my car to get my emissions done to day and it failed for producing to much NOx (nitrogen oxide) failed on both high and low end from what he said but it passed everything else. Now i have asked numerous people taken to a few places and they said that it is more then likely the Cat. what is yalls take? i honestly only haev till the 21st before my tag expires and i need to be able to drive. im like on crunch time. please let me know yalls take! i know every state is different, but im sure info could be of some help

 

[blacknightteg]

Bump

 

[phatintegra]

I failed my beater Jeep for Nox. I replace everything from cat all the way down to the tail pipe and O2 Sensor. Along with a tune up and it pass. Now the state of Maryland banned the Nox test because it's costing them to much money since the newer cars are OB2.

 

[jdmjim]

NOx is caused by high temperature & pressure in the combustion chamber. our cars rely solely on the cat to lower it, but advanced engine timing and a lean fuel mixture will caus high nox. more than likely your cat, but if your co readings are very low, suspect a lean fuel mixture. a lot of times turning back the timing for the test will work.:twisted: