Inspection failure - NOx & CO - BMW Forum - BimmerWerkz.com
3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

 
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#1 (permalink) Old 04-14-2006, 10:37 AM
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Inspection failure - NOx & CO

hey guyz... went for my nj state inspection last week and guess what? it failed..
they said the nox and co levels were too high... i didn't get any check engine lights or anything.. the car runs fine and have no issues..

can you guyz tell me what may be causing this and how i can resolve this issue... don't want to go to a stealership...

btw.. i have a 92' 325i...

thanx
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#2 (permalink) Old 04-16-2006, 12:02 AM
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Carbon Monoxide (CO)*
CO is created when gasoline is not completely burned. High CO ( running rich ).

A list of common causes of CO related smog check failure:

1. Timing is not a big factor in CO production but check it anyway. Everything helps.

2. On older Carbureted vehicles you can have problems like a partially stuck choke plate.This is the moving steel plate on the top of your carburetor.

3. A leaking power valve on your carburetor can cause high CO and Smog Check failure.

4. A faulty carburetor can cause high CO and Smog Check failure.

5. A dirty air filter can cause high CO.

6. A common cause for high CO is a faulty Oxygen Sensor. This sensor tells the computer how to fine tune the air fuel ratio.

7. Other sensors like the M.A.P.sensor , C.T.S. sensor or the Air flow meter can also effect the CO level.

8. A faulty air injection system can cause high CO. This is the Smog pump and related components.

9. A faulty Catalytic Converter can cause high CO and Smog Check failure.

10. If your car has been running rich ( high CO ) you should change your oil after you get it repaired. When you have rich condition all the fuel cannot be burned, you start to saturate the motor oil with CO and HC. This in itself can also cause a rich condition.


Nitrogen Oxides (NOx)*
NOx is formed inside the combustion chamber when excessive heat is present.

A list of common causes of NOx related smog check failure:

1. As usual check the timing first. Advanced timing can cause extra NOx.

2. The next thing to check is the EGR system.This system is designed to reduce Nox. It consists of a EGR valve, vacuum hoses, one or more vacuum switching valves or solenoids. Its job is to reroute a small amount of exhaust gas back into the engine to help reduce combustion chamber temperature. Not all vehicles have an EGR system.

3. Next thing to check is the air / fuel ratio. If the vehicle is running to lean, NOx emissions will increase.

4. Some possibilities are a restricted fuel filter, low fuel pressure, vacuum leaks, oxygen sensor, load sensor such as a map sensor, air flow meter.

5. Check the cooling system. An extra increase in water temperature will increase NOx production.

6. A defective catalytic converter can also increase NOx. The Cat. reduces NOx that has already been produced.

7. Check to see that the air coming into the engine is not over heated. Some vehicles have a vacuum controlled air valve which switches the incoming air to hot air from the outside of your exhaust manifold.This should only happen when the engine is cold. If this system malfunctions and sends hot air all the time.Your Nox could go up. This system is called T.A.C. ( Thermostatic air cleaner )

8. There is another system similar to the one above called E.F.E. ( Early fuel evaporation ). This system routes hot air under the intake manifold. This helps keep the fuel in the vapor state. If stuck in the hot mode Nox emissions could increase and cause a Smog Check failure.


Last edited by SpeedInfusion; 04-16-2006 at 12:04 AM.
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#3 (permalink) Old 05-06-2006, 04:34 AM
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ok so first thing i guess i will do is change the O2 sensor... now i know with the other jap cars in the family, when i had to change this, they asked me if i needed the one before or after the cat...

is there such a thing with bmws? i would presume so... if so, which one should i be asking for in my case since both CO and NOx are relatively higher than they should be?

btw, anyone has the link to the repair manual working again?
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#4 (permalink) Old 05-06-2006, 05:19 AM
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i think i was able to answer both of my questions (one for sure)... i found the manual on kyle's website (thanx dude)... and in the manual it said pre 96 cars had one and post had two..
this is what spring allergies do to you.. keeps you awake at night and makes you post on forums... goodside is atleast i will able to fix something..
cheers...
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#5 (permalink) Old 05-06-2006, 11:21 PM
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Was your car fully warmed up by the time you did the inspection. Most early E36 models have problems with emission levels due to the limited emission control parts, mainly the absence of a egr system causes the high nox. Only remedy for this is to drive the car at high cruise speeds so the cat is basically glowing red hot. I've done smog on a few E36's in CA and this is the conclusion i've come to.


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#6 (permalink) Old 05-06-2006, 11:27 PM
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Quote:
Originally Posted by Ljk619
Was your car fully warmed up by the time you did the inspection. Most early E36 models have problems with emission levels due to the limited emission control parts, mainly the absence of a egr system causes the high nox. Only remedy for this is to drive the car at high cruise speeds so the cat is basically glowing red hot. I've done smog on a few E36's in CA and this is the conclusion i've come to.
hmm thats interesting... ill have to keep that in mind... btw my engine is always blazing hot to the touch even after 30 sec of running... is it just cause its a larger engine then ive been used to?? and will whit effect nox?? oh yeah its not over heating i know that...
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#7 (permalink) Old 05-07-2006, 12:50 AM
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Hey i got a fix for u

Ok My dads corolla had the same problem passing inspection and guess what, he put in injector fluid in the gas tank for like a week and after a week when he had it inspected it was all gone.
it passed the inspection easily with no problems, give it a try, it wont hurt trust me.

regards
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