CA Smog failed due to high NOx
 

I recently failed my smog test in CA. They said that I was fine on everything besides being a couple hundred high on the NOX emissions at 15MPH. What would be the reson for only failing this part of the test? What causes high high NOx emissions. Do those "Gauranteed to pass" thing ever work? THanks for your help.

Running too lean will produce high amounts of NOx. Is your O2 sensor functional?

It would help if you actually gave us DETAILED info about your car.....

If your care is mostly stock, it may be a clogged or disfunctional cat. I had that problem on my car, though i had a catback, intake and ported engine. I replaced me stock cat with a Random Technologies high flow one and i passed smog easily

EGR valve is a possibility
 

The main function of the EGR valve is to reduce NOX emissions by diluting the fuel-air mixture with burned gasses to reduce the peak temperature reached during combustion (high combustion temps cause excessive NOX). Check to see if it's operating properly.

Dave

Of course, not all of our cars have functional EGR valves. Some cars have EGR valves but no connections back to the intake.

just out of curiosity, what are the 15 and 25 mph #'s that you had to get to pass for the nox?

Yeah, EGR reduces oxides of nitrogen, as well as a good cat converter.

heh...we're neighbors, i'm in coto de caza :bigok:
what was the numbers of your NOx reading?


+1

EGR valve maybe a good posibility, however....there might be a relationship with your o2 sensor and also a bad Cat. (which probably blew out cause of your o2 sensor. have your EGR valve tested. as well as o2 sensor and Cat.

is your air pump working? you won't pass smog in california without it.

I don't think the EGR is operative at 15mph. High NOX Is usually the result of higher than normal combustion temperatures + excess air (e.g., lean) or some combination of factors. Ignition timing is also a major factor, might want to check it first. Note that the first brick in the main cat is designed to convert NOX, so it could also be a marginal or failed convertor.

It's my impression that a non-working or missing air pump will actually screw up the A/F ratio. If you look in the manual, you will see that air is injected not only into the cat converter, but in addition is fed into the exhaust ports of the engine, and as a result the O2 sensor "sees" that extra O2. The PCME is calibrated to take that O2 into account, and if the air is not there, the A/F will be wrong.

If/when replacing the catalytic converter, be careful to choose a brand which does not cut corners on the internal distribution of the secondary air. I bought a Bonez aftermarket cat which returned worse results than the old, bad original. Wound up paying for a new OEM cat, which cured the problem and has been OK for the last 3 tests.

Holy crap in a can Batman......how much did that cost you and where did you buy it from?

$1265.62 (discounted from $1406.25)+2 gaskets @ 17.72 total. From Heritage Lincoln Mercury Ford Mazda in Huntington Beach, CA. on 08/09/2002.

You can see why I tried an aftermarket cat first (in addition to new plugs, wires, and O2 sensor, none of which passed)!

There is something to be said for OEM parts, as my stock converter still works after 13yrs. and 156,000 miles... even with mods and running the hell out of it.

anyone know how much you can drop the nox by retarding the timing a few degrees?

:eek: The classified section is your friend. I bet you could have found one with low miles for a benjamin

[QUOTE=SINxSELEKTAH]heh...we're neighbors, i'm in coto de caza :bigok:
QUOTE]

I'm down in RSM as well! :)