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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?
_________________________
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: 24417
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 Offline


Registered: 06/05/03
Posts: 11614
Loc: apple valley, ca
it may be a bad cat. especially an aftermarked cat
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02 Wrangler qsgb 530
87 F250 Diesel proline 1540
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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: 893
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: 1831
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: 4058
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: 1609
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: 6318
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: 34022
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: 201
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: 1601
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.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
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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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#3453871 - 08/12/14 06:49 PM Re: Failed CA emission - high NO [Re: JHZR2]
Jarlaxle Offline


Registered: 02/02/12
Posts: 4206
Loc: New England
Originally Posted By: JHZR2
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.


My Cherokee passed two tests with a cheap part-store cat (Walker, I think) without a problem. And note: the OP's car PASSED twice with the aftermarket cat in place.
_________________________
1979 Coupe de Ville, 542 stroker, parked for winter
1995 Dakota, 5.2, ProLine 5W-30, ProLine
2012 Suzuki AN400A, M1 10W-40, Caltric, parked for winter

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#3453878 - 08/12/14 06:53 PM Re: Failed CA emission - high NO [Re: Bluestream]
Merkava_4 Offline


Registered: 01/30/07
Posts: 9584
Loc: Clovis, CA
Originally Posted By: Bluestream
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


How does the EGR cause a lean condition; is it caused by the EGR valve being stuck open, or closed?

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#3453882 - 08/12/14 06:55 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Chris142 Offline


Registered: 06/05/03
Posts: 11614
Loc: apple valley, ca
part of the smog test is a test of the egr. if the smog guy did his job and did the state mandated test and passed the egr then the egr system should be fine.
_________________________
02 Wrangler qsgb 530
87 F250 Diesel proline 1540
04 Tahoe super-s 530
Z400 maxima 2050
KLR250 Maxima 1040
Polaris Trailblazer delo 5w40

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#3453889 - 08/12/14 07:00 PM Re: Failed CA emission - high NO [Re: Chris142]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Originally Posted By: Chris142
part of the smog test is a test of the egr. if the smog guy did his job and did the state mandated test and passed the egr then the egr system should be fine.


I looked through my past smog tests, they all only show "VISUAL EGR" as a PASS and an N/A to "FUNCTIONAL EGR". It looks like they just check to make sure it's physically there.
_________________________
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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#3453956 - 08/12/14 08:01 PM Re: Failed CA emission - high NO [Re: Merkava_4]
Gokhan Offline


Registered: 12/29/10
Posts: 1601
Loc: Los Angeles, California
Originally Posted By: Merkava_4
Originally Posted By: Bluestream
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

How does the EGR cause a lean condition; is it caused by the EGR valve being stuck open, or closed?

EGR valve doesn't cause lean conditions. It decreases the combustion temperature by recirculating the exhaust gas into the combustion chamber. Decreasing the combustion temperature decreases the NO_x formation, as high combustion temperatures increase the NO_x formation.

Lean conditions (excess oxygen), unrelated to EGR but related to vacuum leaks or fuel-system or emission-component (such as O_2 feedback system) problems, also increase the NO_x, as NO_x is formed by oxygen reacting with nitrogen.

OP might have a carbon-blocked EGR valve or some fuel- or emission-system problems as I mentioned. I had a fully carbon-blocked EGR valve once. The stuff was really, really hard, but I was able to fully clean it with a flat screwdriver (used as a pick) and brake-cleaner solvent.
_________________________
1985 Toyota Corolla LE, 4A-LC engine, ~ 257,000 M
Toyota (by ExxonMobil) SN/GF-5 0W-20 Synthetic
Toyota 90915-YZZF2 filter, 90430-12031 drain gasket

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#3453977 - 08/12/14 08:22 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
artificialist Offline


Registered: 09/23/07
Posts: 6953
Loc: Florida
OBDII cars are supposed to measure EGR flow, show a check engine light, and set a code.

Unfortunately, the system isn't perfect.

The 3800 has a steel tube between an exhaust manifold and the EGR valve. It can easily crack, so feel for gas leaks from that steel tube. Often when you replace the intake gaskets, it disturbs the EGR tube.
_________________________
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#3454501 - 08/13/14 01:43 PM Re: Failed CA emission - high NO [Re: Jarlaxle]
JHZR2 Offline



Registered: 12/14/02
Posts: 34022
Loc: New Jersey
Originally Posted By: Jarlaxle
Originally Posted By: JHZR2
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.


My Cherokee passed two tests with a cheap part-store cat (Walker, I think) without a problem. And note: the OP's car PASSED twice with the aftermarket cat in place.


Wonderful. Dyno tests or just idle sniffers? Make sure youre talking apples to apples and posting numbers before drawing conclusions. My car passed with one of these too. Two years later, not so much. OE converter immediately took it from thousands to single digits, simple as that.

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#3454728 - 08/13/14 06:16 PM Re: Failed CA emission - high NO [Re: Jarlaxle]
Kruse Offline


Registered: 10/05/05
Posts: 3093
Loc: Kansas
Originally Posted By: Jarlaxle

My Cherokee passed two tests with a cheap part-store cat (Walker, I think) without a problem. And note: the OP's car PASSED twice with the aftermarket cat in place.


There are several brands of "cheapie" cats that cannot be installed in several states, for good reasons. A browse through the RockAuto site shows which ones are not for sale in these states. While it is true they may initially pass the test, they usually fail early. Unless it's a beater, a cheap cat can be a waste of money.

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#3454743 - 08/13/14 06:36 PM Re: Failed CA emission - high NO [Re: JHZR2]
Jarlaxle Offline


Registered: 02/02/12
Posts: 4206
Loc: New England
Originally Posted By: JHZR2
Originally Posted By: Jarlaxle
Originally Posted By: JHZR2
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.


My Cherokee passed two tests with a cheap part-store cat (Walker, I think) without a problem. And note: the OP's car PASSED twice with the aftermarket cat in place.


Wonderful. Dyno tests or just idle sniffers? Make sure youre talking apples to apples and posting numbers before drawing conclusions. My car passed with one of these too. Two years later, not so much. OE converter immediately took it from thousands to single digits, simple as that.


IM-240 roller test (tougher than the OP's 2-speed test), passed easily both times. About 65,000 on the cat the second time. Considering the one I had lists for about $100 and an OE cat could run $500+ (if it hasn't gone NS1), it's probably cheaper to use the cheap one even if I DID have to replace it every 2 years.

My Caddy has over 100K on its catalysts...passed its last emission test (also IM-240) last year, about 10% the allowable emissions. (Not bad for 542ci and 3x the factory power...)
_________________________
1979 Coupe de Ville, 542 stroker, parked for winter
1995 Dakota, 5.2, ProLine 5W-30, ProLine
2012 Suzuki AN400A, M1 10W-40, Caltric, parked for winter

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#3454746 - 08/13/14 06:38 PM Re: Failed CA emission - high NO [Re: Kruse]
Jarlaxle Offline


Registered: 02/02/12
Posts: 4206
Loc: New England
Originally Posted By: Kruse
Originally Posted By: Jarlaxle

My Cherokee passed two tests with a cheap part-store cat (Walker, I think) without a problem. And note: the OP's car PASSED twice with the aftermarket cat in place.


There are several brands of "cheapie" cats that cannot be installed in several states, for good reasons. A browse through the RockAuto site shows which ones are not for sale in these states. While it is true they may initially pass the test, they usually fail early. Unless it's a beater, a cheap cat can be a waste of money.


Yes: the manufacturer did not jump through the hoops and spend the money to satisfy CARB, no more & no less. I am very happy I do not have to deal with that idiocy. No, I am NOT choking my Caddy with a dreadful pellet converter to satisfy a bureaucrat!
_________________________
1979 Coupe de Ville, 542 stroker, parked for winter
1995 Dakota, 5.2, ProLine 5W-30, ProLine
2012 Suzuki AN400A, M1 10W-40, Caltric, parked for winter

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#3454989 - 08/14/14 07:13 AM Re: Failed CA emission - high NO [Re: Jarlaxle]
Kruse Offline


Registered: 10/05/05
Posts: 3093
Loc: Kansas
Originally Posted By: Jarlaxle

No, I am NOT choking my Caddy with a dreadful pellet converter to satisfy a bureaucrat!


I guess I haven't seen a pelleted cat since since about 1980 on a GM product. I have an honest question here. Who still makes a pelleted cat?

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#3455183 - 08/14/14 11:20 AM Re: Failed CA emission - high NO [Re: InvalidUserID]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
I keep hearing about cheap aftermarket cats however given that California is super strict about them, wouldn't a cat that is OBD II/CA CARB legal be considered quality?

The cat currently on now is CA-legal CARB certified/approved.
_________________________
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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#3455401 - 08/14/14 02:44 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Chris142 Offline


Registered: 06/05/03
Posts: 11614
Loc: apple valley, ca
the carb approved cat flows just as well as the gofast cat. the carb one has more minerals in it so its cleaner and longer lasting
_________________________
02 Wrangler qsgb 530
87 F250 Diesel proline 1540
04 Tahoe super-s 530
Z400 maxima 2050
KLR250 Maxima 1040
Polaris Trailblazer delo 5w40

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#3455657 - 08/14/14 06:09 PM Re: Failed CA emission - high NO [Re: Kruse]
Jarlaxle Offline


Registered: 02/02/12
Posts: 4206
Loc: New England
Originally Posted By: Kruse
Originally Posted By: Jarlaxle

No, I am NOT choking my Caddy with a dreadful pellet converter to satisfy a bureaucrat!


I guess I haven't seen a pelleted cat since since about 1980 on a GM product. I have an honest question here. Who still makes a pelleted cat?


I have seen them on GM trucks as late as 1995. The OE cat on my CDV would be a pellet type.
_________________________
1979 Coupe de Ville, 542 stroker, parked for winter
1995 Dakota, 5.2, ProLine 5W-30, ProLine
2012 Suzuki AN400A, M1 10W-40, Caltric, parked for winter

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#3455690 - 08/14/14 06:44 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
asand1 Offline


Registered: 12/16/12
Posts: 846
Loc: Oregon coast
"High flow" cat is a misnomer. Pellet cats are a thing of the past. Buy any quality "honeycomb" replacement cat, and it will outflow any OE pellet cat PERIOD.

Quote:
The cat currently on now is CA-legal CARB certified/approved.
Only long enough for one or two tests, then it stops working. "High flow" cats are designed to pass the initial test and then burn out becoming a straight pipe.



Edited by asand1 (08/14/14 06:47 PM)
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#3455720 - 08/14/14 07:07 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Jarlaxle Offline


Registered: 02/02/12
Posts: 4206
Loc: New England
Again, my Caddy has over 100K on its catalysts...passed its last emission test (also IM-240) last year, about 10% the allowable emissions. High-flow cats I think are Magnaflow.
_________________________
1979 Coupe de Ville, 542 stroker, parked for winter
1995 Dakota, 5.2, ProLine 5W-30, ProLine
2012 Suzuki AN400A, M1 10W-40, Caltric, parked for winter

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#3465620 - 08/26/14 06:03 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
UPDATE: Replaced EGR, numbers improved quite a bit at 15 mph but not enough at 25 mph. The car was run about 20 minutes prior, 10 minutes on the highway or so (more on temps later). Here are the numbers on this rescan.



The smog shop suggested I come back in the morning when it's a bit cooler (it was 76f at the time). The smog technician said it looked it was going to pass and then the computer kicked him out and then he had to test again, the second time it didn't look good.

Took it to my mechanic right after and he suggested the same. He was surprised when I told him the shop didn't have the big shop fan on the car during the test, said they are supposed to do so. He asked how long the car was being tested and I said it was on the dyno machine for about 15-20 minutes and idling in between runs. He said the EGR passages were good when he replaced the EGR valve.

Would going in the morning be enough and if not, do I need to look at the cooling system or simply replace the 20k mile cat?


Edited by InvalidUserID (08/26/14 06:04 PM)
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- '97 4.0 Grand Cherokee
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#3466388 - 08/27/14 01:42 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Co-worker of mine asked how the smog went. When I told him about the lack of fan during the smog runs, he thinks that might have had an adverse effect on the numbers as well.

Cooler morning and making sure shop points the fan at the car, numbers improve?
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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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#3466407 - 08/27/14 01:57 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Skid Offline


Registered: 06/10/11
Posts: 201
Loc: USA - Southern California
My guess is that your catalyst is fine because the CO and HC levels are OK. I think the head is running hot.

Did you check your cooling system? I'd suggest changing the thermostat and doing some pressure testing (and changing the radiator cap too). Also check the concentration of coolant - too much coolant, too little water will make the head run hotter. Might help to have the heater running during the test as well, but won't hurt at least.

Also, you wrote earlier that "Cooling system just drained/refilled." Perhaps it wasn't fully burped initially and the higher earlier NOx readings were due to that.

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#3466427 - 08/27/14 02:35 PM Re: Failed CA emission - high NO [Re: Skid]
Bladecutter Offline


Registered: 02/21/11
Posts: 893
Loc: Arvada, CO
Here's all of the OP's smog tests in one shot:





First one from this thread:



And now this one after replacing the EGR:



I find it off that his NOx emissions are so much higher at lower rpms.
The car must be shifting into a lower gear, and then the tester is taking the reading under load to get the NOX scores to increase, yet all the other emissions get reduced under the same conditions.

I still think it's the convertor, since the readings for NOx are all higher after the years, but OP, try dumping a bottle of Techron Fuel system cleaner into your tank, and run through the whole thing as quickly as you can, to remove any combustion chamber deposits that are increasing NOx readings while under load.

Also, when was the last time plugs and wires were changed?
I know with my old '92 Park Avenue, if I didn't change the wires every year, one wire would start shorting to ground under load, and cause a slight miss. That doesn't seem to be the case with your HC readings, but something is causing the NOx to raise up.

BC.
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#3466467 - 08/27/14 03:24 PM Re: Failed CA emission - high NO [Re: Bladecutter]
Skid Offline


Registered: 06/10/11
Posts: 201
Loc: USA - Southern California
Checking the cooling system is much cheaper than changing a catalyst. But it's not my money.

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#3466480 - 08/27/14 03:40 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Thanks for sharing your opinions guys.

Plug wires are relatively new, about 20k on them. Not sure I have enough time to add a cleaner and burn the tank as the sticker expires this weekend. I paid but due to smog fail, it's an incomplete registration. Not sure if I can still get a ticket, don't want to find out.

Re-checked on the coolant: It was flushed and replaced 20k ago but that was about four years ago. Not sure how I overlooked the date in my paperwork. Given how it's four years old, DexCool and that I have/had a very slight timing cover leak, I will get it flushed out and refilled tomorrow at a radiator shop that's fortunately for me, right near a client I'll be at for a few hours.

I have noticed coolant temp gauge taking longer to drop after idling. Not sure if that's related to the NOx and if it is, hopefully a flush and fresh fluid/thermostat takes care of it.


Edited by InvalidUserID (08/27/14 03:42 PM)
_________________________
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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#3466498 - 08/27/14 03:52 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
Skid Offline


Registered: 06/10/11
Posts: 201
Loc: USA - Southern California
Originally Posted By: InvalidUserID

I have/had a very slight timing cover leak...


That would be enough, hence the earlier pressure testing recommendations. My guess - your system is low on pressure because of this leak, and the coolant is boiling at some points in the head (it's like not having a radiator cap). Fix the leak and you'll probably pass.

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#3466708 - 08/27/14 06:59 PM Re: Failed CA emission - high NO [Re: Skid]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Originally Posted By: Skid
Originally Posted By: InvalidUserID

I have/had a very slight timing cover leak...


That would be enough, hence the earlier pressure testing recommendations. My guess - your system is low on pressure because of this leak, and the coolant is boiling at some points in the head (it's like not having a radiator cap). Fix the leak and you'll probably pass.


Didn't think a small leak would have such impact. I noticed a small amount of coolant on my garage floor and took it to my mechanic. He pressure tested it, said timing cover had a small leak. Tried some stop-leak to see if it would work. Not that he didn't want to do the repair or take my money (he didn't charge anything) but wanted to see if the easy fix would work for such a small leak.

Any idea how big of a task that timing cover would be? Want to see if the shop can take care of it and a flush in one shot.
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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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#3468067 - 08/29/14 03:14 AM Re: Failed CA emission - high NO [Re: InvalidUserID]
mehullica Offline


Registered: 08/19/09
Posts: 61
Loc: Modesto,CA
You have a higher than normal level of O2 on your readings. A vacuum leak or lean mixture will raise the O2 levels. Your HC & CO are decent which means you're not having a catalytic converter issue. I think your engine has a small vacuum leak causing a run too hot & fail for NOx. Can you check your O2 readings with a scantool or the obd port with a voltmeter?

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#3468264 - 08/29/14 10:20 AM Re: Failed CA emission - high NO [Re: mehullica]
InvalidUserID Offline


Registered: 08/23/04
Posts: 630
Loc: Bay Area, CA
Originally Posted By: mehullica
You have a higher than normal level of O2 on your readings. A vacuum leak or lean mixture will raise the O2 levels. Your HC & CO are decent which means you're not having a catalytic converter issue. I think your engine has a small vacuum leak causing a run too hot & fail for NOx. Can you check your O2 readings with a scantool or the obd port with a voltmeter?


Yes, I have an OBD II scanner. What data should I look at?
_________________________
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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#3468673 - 08/29/14 05:46 PM Re: Failed CA emission - high NO [Re: mehullica]
paulo57509 Offline


Registered: 07/13/03
Posts: 1831
Loc: Tracy, CA
Originally Posted By: mehullica
You have a higher than normal level of O2 on your readings. A vacuum leak or lean mixture will raise the O2 levels. Your HC & CO are decent which means you're not having a catalytic converter issue. I think your engine has a small vacuum leak causing a run too hot & fail for NOx. Can you check your O2 readings with a scantool or the obd port with a voltmeter?


I think '96 Camaros have an air pump (electric) that introduces additional air into the catalytic converter. If an air pump is present, there will always be excess O2 present.
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#3470048 - 08/31/14 12:23 PM Re: Failed CA emission - high NO [Re: InvalidUserID]
mehullica Offline


Registered: 08/19/09
Posts: 61
Loc: Modesto,CA
Look at your o2 voltages at 2500 rpm on a hot engine. Look at the voltage changes to see if they are switching above & below .5 volts at least a few times a minute. Then let it idle & watch the voltages. Should be above .6-.75 volts at idle with little or no switching under .5 volts.

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