Automotive Forums  Where Car Enthusiasts Go to Discuss Cars Online

Good morning all - I'm trying to get my Pathfinder to pass smog.  I am a bit of a car novice, but have repaired a few minor items on my own.  Thing is, I've spent quite a bit of money already to get this car ready (had a check engine light on for a broken speedo head). And I'd like to pick your brains a bit and see if there are some obvious items I can do before spending a couple hundred more dollars for a repair.

My recent smog test failed, but only on one item.  And that is the NO (PPM) test at 15mph.  There is a max of 501 PPM for my vehicle and it measured at 664 PPM.  Everything else passes easily.

Is there anything I can try on my own (that's not too intense for a novice) to reduce the NO?

Thanks in advance for any help!