I just took a smog test in CA and I failed it because of high NoX, any ideas how i can solve it? I have a stock CAT, after market exhaust, spark plugs were changed recently.

 

Make sure your EGR is working properly.

 

Thanks!

Yup EGR is working fine.

 

Besides a CEL it might not open or close all the way thanks to the crud that builds up on the valve. If the EGR is not fully open you can fail a Nox test easy, especially in the recent heat.

 

They actually do the sniffer test in CA?!

 

I believe you can determine abnormally high amounts of NOx through the OBD system.

NOx is created because of high (or excessive) combustion temperatures. You should scan for any codes; this might help you determine your exact problem.

 

Just scanned for codes, no codes either. Yeah.. CA takes readings at 15mph and thne at 25 mph.. those bassards!

 

+1 for what keeps being said. IIRC around 2500 + degrees fahrenheight.

Almost always EGR related, unless you have other engine issue. (misfire, lean condition, preignition, etc.)

First thing I would do is double check and make sure your egr system is working.

 

Thanks! I'll give it a shot.