Emissions/NOx levels

[benjawi4]

As I mentioned in another thread (and yes, I'll stop cluttering this great forum with question after question, I promise), I have failed two emissions tests here in CO in two days.

Yesterday my rig failed due to a faulty gas cap. I replaced the cap this morning, but unfortunately the rig failed the emissions test again due to high NOx levels (2.00 is the max allowance).

My question is, does anyone have any idea why my NOx levels would jump from 1.71 yesterday to 2.41 today? I'm purplexed. In the past month I have not only replaced both exhaust manifolds but the muffler as well.

Any thoughts?
Thanks friends,
Ben

 

[04UZJ100]

Were you at full OP temp for the test?

 

[benjawi4]

I thought I was, but in retrospect the last 15 or so minutes of my commute was stop and go traffic. I've read up on common issues, however I haven't been able to find anything addressing such a drastic change in less than 24 hours. I'm going to try again on Monday morning, choosing a testing site roughly one hour away (hour of driving at 72mph should have her ready for a good test...in theory).