nicole89

I've replaced the catalytic converter, egr valve, and the electronic control module. I even ran some seafoam through it.
HC: 2.37 (passing standard: 1.60)
CO: 7.52 (standard: 15.00)
NOX: 2.61 (standard: 2.50)

After I got the catalytic converter my HC passed and my NOX was over by .04, and it went up after I got the new egr valve and electronic control module.

I bought new spark plugs but have yet to put them in. Does anyone have any tips or thoughts? Also why would my levels go up so much after getting work done?

ASE doc

High NOx is caused by high combustion temps. Anything that affects combustion temperature, lean afr, too much timing, poor cooling system function, wrong spark plugs, EGR not working, will cause NOx. High HC with high NOx sounds like a lean condition or too much timing advance. Look for any air leaks in the intake. Retarding the timing 2 degrees will reduce both. You can put it back after you pass the test. The main function of the EGR valve is to reduce NOx by reducing combustion temps. Make sure it's working. The valve is only one part of the system. Make sure the passages are clear and that the control solenoid is working. If in doubt you can bypass the solenoid for the test. At idle, the engine should stall if the EGR valve is opened by hand. If the engine doesn't stall, or at least severely fall on its face, the passages need to be cleaned.
The catalytic converter when working right reduces HC by about 200 to 300 ppm. It has less effect on NOx. By the sound of this, I guess you are having to test on the wheel dyn and not just at idle. If the test is just at idle, remember that a colder engine produces little or no NOx.

punkmaster98

iTrader: (5)

i failed for the same thing. I found out it was my o2 sensor. I had a nonheated o2 and when the car sits idling (waiting in line for inspection) the sensor cools off and would run rich, and i failed. I replaced it and passed with flying colors

TA

iTrader: (1)

I and several others have also failed because an old cap and rotor were arcing causing a misfire. Everything else can be right, but as tight as the specs for our cars are now, one thing will put you over the limit, so just throwing parts at it can be pretty expensive.