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#3453682 - 08/12/14 03:55 PM Failed CA emission - high NO
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
My '96 3.8L Camaro failed it's first California emission test. It's gotten near the maximum allowed before but that was a HC issue which wasn't an issue this time. This time it failed due to high NO numbers.



I don't have any CEL or any rotten smells coming from the car. Mods are an intake, headers, high-flow cat and exhaust system but I've had all those the past 2-3 checks and haven't seen numbers like this. The NO numbers were about half in the two previous emission checks.

Where to start? Plugs, wires, fuel filter, O2 sensors, etc are all under 2 years and less than 12k old. Cooling system just drained/refilled. The EGR valve, as I understand, might be a culprit and it's probably near 8 years old and 80k on it though again, no CEL.

What else would contribute to a doubling NO test count?
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My Cars aka 'ol reliables:
- '96 Camaro 3800 II
- '97 4.0 Grand Cherokee
- '99 Civic EX

Others I service:
- '01 Mustang, '04 Accord V6, and '93 Saturn SL2

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#3453687 - 08/12/14 04:00 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
eljefino Offline


Registered: 06/15/03
Posts: 24654
Loc: ME
EGR likes backpressure. Root out the passages. Cool the engine off... rad flush.


Edited by eljefino (08/12/14 04:06 PM)

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#3453690 - 08/12/14 04:06 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Chris142 Online   content


Registered: 06/05/03
Posts: 11751
Loc: apple valley, ca
it may be a bad cat. especially an aftermarked cat
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#3453706 - 08/12/14 04:19 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Found info on the cat. Carsound cat, installed in '08, approx. 20k on it.
_________________________
My Cars aka 'ol reliables:
- '96 Camaro 3800 II
- '97 4.0 Grand Cherokee
- '99 Civic EX

Others I service:
- '01 Mustang, '04 Accord V6, and '93 Saturn SL2

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#3453710 - 08/12/14 04:22 PM Re: Failed CA emission - high NO [Re: Chris142]
Bladecutter Offline


Registered: 02/21/11
Posts: 907
Loc: Arvada, CO
The entire EGR system should be inspected.
Also, how hot was your car before the test?
This is important for NOx.

If the EGR system isn't plugged or have a bad component, then you will need a new convertor.

BC.
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#3453711 - 08/12/14 04:26 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
paulo57509 Offline


Registered: 07/13/03
Posts: 1840
Loc: Tracy, CA
Typical and common things to consider:

Vacuum leaks, lean mixture, over advanced timing, in-operative EGR valve, plugged or partially plugged EGR passages, aftermarket non-CARB converter.

I'd look at the EGR system first.

I'd put a lean mixture down on the list of things to look at. You do have excess O2 but I don't think it's enough to affect the NOx readings.

If you have your previous year test results, it might help to compare the measured numbers. Perhaps there's a trend that might point you in the right direction.

I'd throw in the time table of when you made the engine mods for comparison purposes as well.


Edited by paulo57509 (08/12/14 04:27 PM)
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#3453712 - 08/12/14 04:27 PM Re: Failed CA emission - high NO [Re: Bladecutter]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Originally Posted By: Bladecutter
The entire EGR system should be inspected.
Also, how hot was your car before the test?
This is important for NOx.

If the EGR system isn't plugged or have a bad component, then you will need a new convertor.

BC.


Should have added that info about temperature.

I had driven the car on the highway about 30 miles to the testing shop. It was shut off for approx. 5 minutes before they put it on the machine.

Is it likely the EGR valve or cat?
_________________________
My Cars aka 'ol reliables:
- '96 Camaro 3800 II
- '97 4.0 Grand Cherokee
- '99 Civic EX

Others I service:
- '01 Mustang, '04 Accord V6, and '93 Saturn SL2

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#3453723 - 08/12/14 04:40 PM Re: Failed CA emission - high NO [Re: paulo57509]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Originally Posted By: paulo57509
Typical and common things to consider:

Vacuum leaks, lean mixture, over advanced timing, in-operative EGR valve, plugged or partially plugged EGR passages, aftermarket non-CARB converter.

I'd look at the EGR system first.

I'd put a lean mixture down on the list of things to look at. You do have excess O2 but I don't think it's enough to affect the NOx readings.

If you have your previous year test results, it might help to compare the measured numbers. Perhaps there's a trend that might point you in the right direction.

I'd throw in the time table of when you made the engine mods for comparison purposes as well.


Engine mods were in '06 so I've had three passing emission tests since then.

Dug up the last three emission tests, NO is really the only thing that has consistently been high.

2008: 15mph measure was 394, max is 424. 25 mph measure was 138, max is 711.
2010: 15mph measure was 209, max is 424. 25 mph measure was 312, max is 711.
2012: 15mph measure was 159, max is 424. 25 mph measure was 248, max is 711.

Since it's such a rarely driven vehicle, I haven't had to change much on it due to mileage.

Cat is CA legal, made sure that part was kosher before I purchased it.
_________________________
My Cars aka 'ol reliables:
- '96 Camaro 3800 II
- '97 4.0 Grand Cherokee
- '99 Civic EX

Others I service:
- '01 Mustang, '04 Accord V6, and '93 Saturn SL2

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#3453750 - 08/12/14 05:04 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Bluestream Offline


Registered: 09/13/03
Posts: 4114
Loc: Waterloo, ON
Higher than normal NOX emissions may be caused by:
-an overheated engine
-Lean air/fuel mixtures
-Vacuum leaks
-over advanced ignition timing
-Defective EGR system
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#3453761 - 08/12/14 05:14 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
EricF Offline


Registered: 07/14/09
Posts: 1611
Loc: SF Bay Area
The EGR is the first place to look at.
Probably just needs a very good cleaning, not just the valve, but all the ports, hoses and lines. hose them with carb spray.
A good run on the freeway would definetely help break that stuff up too.

I'd also do a seafoam de-carbonization and also a good freeway run.

I wouldn't be to concerned with the cat being faulty at this point. Your HC's are very low and CO is next to nothing.
This really is pointing to a plugged up EGR system.

Looking at
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#3453785 - 08/12/14 05:37 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
901Memphis Offline


Registered: 08/14/10
Posts: 6356
Loc: Northern Kentucky
CRC Guarenteed to pass? High PEA content, won't hurt!
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#3453797 - 08/12/14 05:52 PM Re: Failed CA emission - high NO [Re: Chris142]
JHZR2 Offline



Registered: 12/14/02
Posts: 34230
Loc: New Jersey
Originally Posted By: Chris142
it may be a bad cat. especially an aftermarked cat


Agreed. My 318i doesnt even have EGR. Failed NOx once, replaced it with a Magnaflow, barely passed. Replaced it with an OEM one, and passed with flying colors...

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/915639

ONLY EVER BUY OEM if you plan on doing anything besides dumping the car.

I learned that at my own expense. The aftermarket cat was barely good enough to improve numbers compared to my OE cat which was not converting NOX. New OE, NOx was at 7. All the other measured items had substantial improvements percentage wise but nowhere near the swing in number values.


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#3453814 - 08/12/14 06:04 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Skid Offline


Registered: 06/10/11
Posts: 209
Loc: USA - Southern California
I thought you generally didn't have to go on the rollers in California anymore for year 2000+ cars. Just visual inspection and a code check.

Anyway, pressure check your cooling system and check for leaks. A hot cylinder head will raise NOx.



Edited by Skid (08/12/14 06:05 PM)
Edit Reason: whoops... didn't realize it was a '96.

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#3453824 - 08/12/14 06:13 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Gokhan Offline


Registered: 12/29/10
Posts: 1609
Loc: Los Angeles, California
Leaner mixtures result in higher NO_x and lower HC. Richer mixtures result in lower NO_x and higher HC. If you can adjust the mixture, do so.

Check the EGR system, which reduces the NO_x. See if it's working. If it's not working, it could be because of an EGR valve blocked with heavy carbon deposits or a torn EGR-vacuum-modulator diaphragm. Carbon deposits on the EGR valve can be removed using a flat screwdriver as a pick along with a brake-cleaner solvent.

In your car, the most likely candidate is the carbon deposits on the EGR valve. It also doesn't seem to have an EGR vacuum modulator but a solenoid. So, check if the solenoid is working as well.
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#3453869 - 08/12/14 06:47 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Thanks for all the input everyone. I've never failed an emission test before (come close, but never failed) so it's something new to worry about.

I've had the car for the last 14 years and 140k miles and haven't cleaned any EGR related items, just replaced the valve many many years ago. Come to think of it, I don't think I've ever replaced any vacuum hoses/lines either.

And in case anyone else is a visual person like me, here are the previous three passing tests.



_________________________
My Cars aka 'ol reliables:
- '96 Camaro 3800 II
- '97 4.0 Grand Cherokee
- '99 Civic EX

Others I service:
- '01 Mustang, '04 Accord V6, and '93 Saturn SL2

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