Failed CA emission - high NO

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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.
 
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.
 
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.
 
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...)
 
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!
 
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 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.
 
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.
 
"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.
 
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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.
 
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.

24pm7er.jpg


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?
 
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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?
 
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.
 
Here's all of the OP's smog tests in one shot:

21lrk9z.png

ntkih.png

j0jjib.png


First one from this thread:

biwl1k.png


And now this one after replacing the EGR:

24pm7er.jpg


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.
 
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.
 
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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.
 
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.
 
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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