Calif Smog Test Question

[E30 Cabrio]

When I bought my car 2 years ago, the Smog Check showed that the NO (Nitrogen Oxide) levels were high - right near the limit, but the car passed.

Now, 8,000 miles later, I'm due for a retest and was wondering what I could do to lower the levels of Nitrogen Oxide.

[Danny]

New Cat.

[Jon325i]

New Cat.

True - very likely. But I like to refer to that as "plan b". Before taking the car in for the sniff test, do the following.....

Change engine oil & filter

If you have a performance chip in the ECU, re-install the stock chip

Check your 02 sensor - it may need to be replaced if its been in use for a while. FYI - there are two versions (3-wire & 4-wire) - make sure you get the correct replacement if you change this out

Run 87 octane fuel

Buy a bottle of CRC brand "Guaranteed To Pass" - follow the directions exactly!

You might want to try using a technique called SeaFoam. There's a lot of information about this process on this site, just do a search. I did all of the above and have been able to pass the smog test with a catalyst converter which had many, many years of use on it.

Hope this helps.

Jon

[Danny]

Run 87 octane fuel

Why 87?

Wouldn't 91 do better?

[shiftbmw]

Drive the shit out of it for the 30 minutes before you test and don't wait around and let it sit at all before they hook it up. If they have you waiting, drive around the block a few times. Get that cat nice and hot.

[Jon325i]

Why 87?

Wouldn't 91 do better?

Higher octane grade fuels burn hotter - this can effect the emissions readings at test time. You want the catalyst to be super hot when you test it.

[Danny]

Higher octane grade fuels burn hotter - this can effect the emissions readings at test time. You want the catalyst to be super hot when you test it.

So wouldn't 91 be better?

[JPL]

make an adjustment to the afm to make it run slightly richer mix.

I recently just passed smog after the first test when my NO was at 2600. Changing the mix brought me down to 200 which is way under the 760 limit. It also didn't effect the CO enough to make me fail that just don't make it too rich.

[SpecM]

Higher octane grade fuels burn hotter - this can effect the emissions readings at test time. You want the catalyst to be super hot when you test it.

I think you contradicted yourself...

and higher octane fuel burns cooler iirc

[FLUTE007]

NOX is caused by the car running hot, if you want the nox to be lower make sure that the thermostat and aux fan are in proper working order. if they are not cooling the engine properly the nox levels will be high. try to go on a cooler day if that is possible

[E30 Cabrio]

Damn, now I'm confused. Hot? Cold?
BTW, how do I adjust the AFM to make it run richer and how much is too much?
I'm going to get the CRC additive and swap out my chip for the stock one, but should I run 91 Octane?
Bring it to the shop Hot or Cold?
Thanks.

[FLUTE007]

normal operating temperature, make sure it doesn't run hot

[clavinZERO]

DO NOT mess with the AFM unless you can set it properly with some sort of emissions reading tools... It has to be adjusted with the o2 sensor off and then you have to watch the air-to-fuel ratio as you adjust. This is not something you just tweak a lil bit.

[E30 Cabrio]

normal operating temperature, make sure it doesn't run hot

My Fan CLutch might be going bad because if I let the car idle for several minutes on a hot day, like 90+, the temp needle will move a little above the halfway mark.

It's supposed to cool down this week, so I will probably drop the car off at the smog place because it's near work, walk to work, have them smog it and hope it passes.

I'm going to change the plugs and oil and oil and air filters, plus run the CRC additive.

So I should have them smog it when the car is cold if my NO levels are high?

And Premium or Regular? I still need to swap my chip as well.

[s0urce]

Drive the shit out of it for the 30 minutes before you test and don't wait around and let it sit at all before they hook it up. If they have you waiting, drive around the block a few times. Get that cat nice and hot.

Exactly! This works like a charm.