Emissions Failure

I just ran the car through the NJ Inspection Station and much to my surprise it failed the emissions for NOx (1700 v. the max 1262). Everything else was within spec and, when I looked at my previous test sheet she was under the 1200. Before I go swapping out cats & O2 sensors etc, can anybody give me some direction regarding the likely cause of excess Nitrogen Oxide emissions.
Thanks, Jim.

If you have an EGR, that's the thing to look at. If not, and you have and AOD, then look for vaccuum leaks. My Nox was slightly over when I noticed that the PCV breather tube was unhooked. This affected the amount of intake air just slightly in that the additional air wasn't measured by the MAF.

After that, have your cats tested at any muffler shop. They take a temperature reading and will know if they're working OK. On the AOD, the 3way cats are what reduce Nox. O2 sensors have very little to do with it.

High NOX readings are caused by elevated combustion chamber temps. Something has raised the combustion chamber temps.
Check for vac leaks and EGR if you have it.
Have you done any internal engine mods?........or it could be the cats.

i was at the Canfield Road inspection in Randolph NJ

my Nit Oxide was high as well.. There's what you do... check the PCV VALVE if it's an aftermarket one from (Pet Boys, Strauss, etc.) change it to a MotorCraft NJ is notorious for failing us with Aftermarket PCV Valves cuz the equipment is so sensitive...

Then check for leaks i'm sure you'll pass

Could still be CAT's.

Here in Riverside is about the toughest SMOGG region in CA (it backs up here from the LA basin in the summer). I DID have to replace the CAT's to pass NOx.

Lee

Failed NO test in California

Hi, guys;
I know this is an old thread, but now California has added the NO tests to its smog testing.

1) What is "CATS"? Catalytic converter? I had one of them replaced about 3 years ago, but the other one is old.

2) I just had my 89 SC fixed; the idle speed was messed up, and it turned out to be the idle speed motor, which was replaced. Could this have anything to do with my failure?

Thanks for any help you could offer,
Fred
San Jose, CA

1. Cats = Catalytic Converter. Generally they last a long time, like 150,000+ miles.
2. The idle speed won't affect your emissions test if its a dyno test.

If your car is equipped with an EGR (discussed above), those usually don't last forever and can cause high Nox.