Failed smog, high nox

[jw123]

My Delorean failed the CA Smog test because of high nox

max ave measured
15mph 1148 419 1337
25 mph 978 350 1119


Does anyone have an idea of what may be causing this high nox reading? All other elements of the smog test passed. It seems to be running really well.

I do have Seafoam in the fuel mixture at this time, could that have anything to do with it?

[Ryan King]

What type of exhaust system do you have? This isn't uncommon for us CA residents to fail due to NOX.

Last Year I had to through an extensive process to pass....
I took the car in without doing anything to it to a local shop about 10 miles away. FAILED.

So I did some work to the car...

1. Aired up the tires to 40 PSI
2. Changed the Oil
3. Cleaned the Air Filter
4. New Exhaust Gaskets
5. Took off my dual cats (I have Stage II) and soaked them overnight in Laundry Detergent and Water.
This supposedly helps to break down all the residue buildup in the "honeycombs" of the CAT. Thus resulting in a cleaner burn.
6. I also made a 40 mile treck (One way) to a Smog shop in Visalia. Getting the engine nice and warmed up helps with good results.
7. Also filled my tank up with Premium gas for a cleaner burn.
8. Adjusted my Dwell

I couldn't tell you specifically what did the trick, but my numbers were greatly reduced and I passed.

Ill do it ALL over again next year....*sigh*

Here are my reports for Reference -

Before all the work mentioned above - (Fail)
35402

After all the work mentioned above - (Pass)
35403

15 MPH
1309 on the Failed Report
1097 on the Pass Report

25 MPH
720 on the Failed Report
943 on the Pass Report

Another forum member here Tom Tait failed not too long ago too. Here is his quoted from another thread

Took rear tires up to 50 PSI to reduce rolling resistance. Added a coolant additive to make the coolant more efficient at transferring heat, and requested the tech use the cooling fan during the test. U did not get the car as hot this time - we tested at about 210 degrees, on the gauge instead of 225 as I did last time.

My other gasses did go up, but my NOX went way down, and I still passed.
I assumed I would fail, I just went in to get an incremental report today for additional data before soaking the cat - but with a few simple changes - I passed. Science wins again!

[fnzen]

My Delorean failed the CA Smog test because of high nox

max ave measured
15mph 1148 419 1337
25 mph 978 350 1119


Does anyone have an idea of what may be causing this high nox reading? All other elements of the smog test passed. It seems to be running really well.

I do have Seafoam in the fuel mixture at this time, could that have anything to do with it?

Your cat is going bad

[Ryan King]

Your cat is going bad

I would say before deeming a CAT bad, first try and fix it. Soaking it is a free method and worth a shot before jumping to the bad conclusion.

[David T]

I would say before deeming a CAT bad, first try and fix it. Soaking it is a free method and worth a shot before jumping to the bad conclusion.

I don't know about soaking the cat in laundry soap. There are additives that are sold that you add to the gas tank that are supposed to burn up the contaminants in the cat. Also I like Techron to clean the injectors so you get a good spray pattern.

[Jonathan]

I don't have any experience with this California emissions testing stuff, but the mention of pumping up the air pressure in the tires made me think of something...

If you knew what the calculation was, and wanted the answer of that formula (the NOX number) to decrease, you can lower the numerator or increase the denominator, right?

What made me think of whether the tire pressure is helping or it isn't, won't affect the engine performance individually, but if the better (lower) rolling resistance happened to improve (increase) the portion of the formula in the denominator, it could be helping in a significant way.

I am thinking if the math calculates your emissions "per mile" or something like that, and the per mile calculation is based on the rear wheels spinning in the dyno and that translates to an assumed distance travelled, yada, yada, yada, you might kind of fool the test to think you travelled further during the test than you did and thus spreading out the emissions over a longer distance resulting in a lower "per mile" number than what it might really be in the real world (that same real world where you're idling your minimally polluting DeLorean beside some poorly maintained, black soot spouting truck in the lane beside you, but I disgress...). Or just sneak on some bigger tires for the afternoon and hope they don't notice...

Just a thought :)

[berickson926]

My car was failing NOX for CA smog, DMC-CA helped me get the car to pass. Ultimately it needed a new cat.

Before:

15 MPH - 1585
25 MPH - 1408

After:

15 MPH - 978
25 MPH - 616

[PJ Grady Inc.]

My car was failing NOX for CA smog, DMC-CA helped me get the car to pass. Ultimately it needed a new cat.

Before:

15 MPH - 1585
25 MPH - 1408

After:

15 MPH - 978
25 MPH - 616

High NOX is almost always a bad cat as reducing NOX is one of it's main functions. I question too David the viablity of washing the contaminents away.
Rob

[Ryan King]

High NOX is almost always a bad cat as reducing NOX is one of it's main functions. I question too David the viablity of washing the contaminents away.
Rob

My only argument is its worth a try. I wasnt going to spend 800+ for two new catalytic converters before trying the soaking method. Maybe it didn't work, maybe it was one of the other things I tried that did the trick. But accumulatively, it passed whereas before it failed. I can't cheat the numbers, they are right there.

[TTait]

Here is your best shot with 1 hour of work and minimal investment -

Take the pressure in the tires up and do your fluid changes etc, good gas, seafoam cycled out, running well, ac off, no accessories on, - then go back for another smog test.

With High NOX you are looking to run the rest with a cooler system - NOX is partially a byproduct of a very hot system. We are lead to believe that when testing hot engine is better - depending on your test results that's not always true. I did this a few months back and retested with a warm, but not hot engine. My CO came up, but my NOX came way down and I passed.

Higher temps gets you lower CO but higher NOX, medium temps get you higher CO but lower NOX.

You may need to do more - you will need a cat someday - washing out the cat may help - or not. Doing this is cheap and easy - try it first running a little cooler and you may be okay, at least for two more years.

[bxtech]

I was also skeptical of cleaning a cat with laundry detergent, but I thought......What the heck? What have I got to lose!? I had the issue on my Toyota and since I was removing the cat anyway, I gave it a shot. I have to say that it did work and it brought down the emissions a fair amount. I was pretty impressed. However, in my case it didn't bring down the numbers enough and I ended up having to replace the cat anyway. Later on, I opened up the old cat and found that a decent amount of the media was actually broken which is why it obviously wasn't working up to efficiency. However, washing it definitely helped and made the cat perform better than before. I can vouch for that fact, at least in my case.

Check out the vid on youtube:

https://www.youtube.com/watch?v=5icTmYItwiE

[fnzen]

I would say before deeming a CAT bad, first try and fix it. Soaking it is a free method and worth a shot before jumping to the bad conclusion.

If you wash crap out your cat to pass it WAS and IS going bad

memba cats catch crap its what they do at some point its just full of crap!