The car in question is a 2007 Nissan Altima. It is confirmed by Nissan to be a Cali spec car, even though its lived its whole life in Delaware.
It was run for a very long time with a CEL/ P0420 code caused by a torn air intake duct.
The upstream O2 sensor was replaced, along with the duct and spark plugs. The old O2 sensor was white and funky looking when it came out. It looked very much like a spark plug from an engine running very lean.
Afterward, the car ran a lot better, but not as well as it should, according to the owner.
The fault code came back a few days later. I'm going to go scan the code later today to see if its the same code, also I now have a scanner that read sensor outputs in real time, so I can take a good look at the downstream sensor. I fear the Cat is toasted though.
My questions are, can a severely lean condition ruin a catalytic converter, and is a Cali spec Cat required on a Cali car outside of the People's Republic of California? IE, if a standard Cat is used, will the CEL stay on forever?
Deleware's neighbor, New Jersey, is a Californa state, so all cars that are sold there are to the CARB standards- so it's highly likely the car came from there.
If the lean causes a misfire, yes, that will damage a catalyst very quickly. Unburt fuel plus fresh air makes a lot of heat.
I'd bet that it's damaged pretty badly.
As for a cat change- the calibration expects to see the original catalyst there, so if you put a lesser one in, it could be unhappy. I doubt it would really notice for 100k miles though. A fresh lighter loaded cat looks very much like a higher loaded cat for quite a while to the monitor.
A better question is- can you get a Federal spec catalyst that will bolt right in there? And if not, will the cost to change the entire system over be more than just getting the original spec catalyst.
And then an even better question- are you doing this work? It's quite possible that a shop will look at the VIN number and see that it's a CARB spec car, and being that it's not legal to change it, just get the CARB cat anyway.
Lean running is much worse on cats than rich because the extreme heat will melt it internally.
That being said, be very careful. Since the cat is mounted on the manifold, when they break down the particles make it back into the combustion chambers completely destroying the rings and cylinder walls. The 2 Altimas that came in to my shop with bad cats needed engine replacements
BTW-when I was shopping for catalyst replacements for my neighbors CA Infinit i30, there were non CARB legal cats available for CA emmision vehicles. So they were tuned for CA emmisions, just didn't meet CARB standards. Sounds like they were meant for this type of situation.
Cone_Junkie wrote:
Lean running is much worse on cats than rich because the extreme heat will melt it internally.
Uh, not so much. The hottest the exhaust gets- just barely lean of stoich. Leaner than that, and the exhaust temp drops really fast.
just pointing that out.
California-legal cats are more or less a quality spec. Simply put, a lot of aftermarket cats are garbage that will sometimes fail NOx when new, and usually fail for NOx after two years. So California stepped in and basically said, okay, it's pointless to put junk new cats on cars, so we will have a minimum spec.
Having fought cheap cats and the cheap car owners who buy them then still can't pass emissions, I am for this.
In reply to Knurled:
Many california spec catalysts also have more precious metals on them. So that they can meet the mostly lower california rules. So a PZEV Altima will have a much more expensive catalyst than any other version of it.
not all, plus many cars are 50 state certified- so a federal car is the same as a CARB car.
In this case, I see that there are two california certs and one federal- a PZEV, a LEVII, and a Tier 2 Bin 5.
it's pretty common to see a LEVII/T2B5 cert that is one car- and looking at the cert data, I'd have to say it's one car.
So confirm that the car isn't PZEV (it should say on the cert sticker) and a federal catalyst will be the same as the california one.
(BWT, I use this page a lot for cert data- http://www.epa.gov/otaq/crttst.htm lots of good data there)
In reply to Cone_Junkie: would a compression test show the damage that your talking about? The car doesn't smoke and runs smoothly.
In reply to alfadriver:
Thanks for the insight. I see that Rock Auto has a Cali spec Cat at a reasonable price.
Also, since you are in the business, do think that there is any chance that this Cat could still be in warranty?
In reply to HappyAndy:
Could be, I think the warranty is 8y/80k miles. Worth checking.
Cone_Junkie wrote:
Lean running is much worse on cats than rich because the extreme heat will melt it internally.
In the old days a stuck closed choke would cause the converter to glow red, you can't get much hotter than that.
alfadriver wrote:
In reply to Knurled:
Many california spec catalysts also have more precious metals on them. So that they can meet the mostly lower california rules. So a PZEV Altima will have a much more expensive catalyst than any other version of it.
Well, sort-of. Even a Federal emissions car will emit cleaner air than the engine takes in once the cat lights off. The difference between Cali and 49-state is how quickly the cat can light off, when looking at new cars. So California-spec emissions tend to have air pumps while 49-state don't. (At least, this is my impression from living in a Federal-emissions state but having to deal with California-spec cars on occasion)
As far as aftermaket cats go, yes, the CARB-legal ones have more precious metals. Because the ones with less precious metals are garbage in ALL states. California is simply the state that put their foot down with regards to the sale of garbage cats.
Knurled wrote:
alfadriver wrote:
In reply to Knurled:
Many california spec catalysts also have more precious metals on them. So that they can meet the mostly lower california rules. So a PZEV Altima will have a much more expensive catalyst than any other version of it.
Well, sort-of. Even a Federal emissions car will emit cleaner air than the engine takes in once the cat lights off. The difference between Cali and 49-state is how quickly the cat can light off, when looking at new cars. So California-spec emissions tend to have air pumps while 49-state don't. (At least, this is my impression from living in a Federal-emissions state but having to deal with California-spec cars on occasion)
As far as aftermaket cats go, yes, the CARB-legal ones have more precious metals. Because the ones with less precious metals are garbage in ALL states. California is simply the state that put their foot down with regards to the sale of garbage cats.
Sorry, Knurled, but no sort of about it. The whole reason PZEV cars light off faster is due to the higher loading of the precious metals, and sometimes due to the more expensive higher density cells of the catalyst. That, and being that there is less room for problems, most PZEV's have to be a little cleaner all of the time- thus more expensive hardware.
Not all PZEV's have air pumps, as it's cheaper to put more more money into the catalyst than an air pump. F's first solution had air pumps, and all of the subsequent have not. While I don't speifially know about 2007 PZEV Altimas, I would bet that it does not have an air pump.
One other big thing about PZEV vs everything else- it's a 150k requirement vs. a 120k requirement. And to make the system robut to aging, again, more metal it put on them.
This is all from an OEM standpoint. I have no idea about the aftermarket, exept that their requirements to be allowed is a lot easier than an OEM- whereas OEM's have to prove durability and low level capabilty over a wide range of samples, aftermarket ones do not- they just have to prove basic capability. I'm not even sure IF they have more metal, as none of them tell you what is on them. But I DO know that OEM's use more metal- most of them have been analyzed.
You're missing the forest for the trees, here.
The reason why California felt the need to impose legislation regarding aftermarket cats, is a lot of aftermarket cats have so little precious metals in them that they are not effective at cleaning emissions, period. That $69 catalyst that ***co made is technically a cat but it doesn't work like one. Not well enough to actually do the job it is intended to do.
This isn't a California va. 49 state emissions standards thing. This is a California bothering to legislate aftermarket parts quality thing.
OK, back on topic. The only code it had today is a P0420. Using my torque app, I drove it around in varying conditions with the output voltage of all 3, (yes 3), O2 sensors graphing. Sensor #1, the one that was replaced, has a pretty steady output voltage.
#2 is swinging from the top to bottom of the graph. The torque app is putting a red circle around the high voltage peaks on the graph (.08v/.09v). I'm still learning how this app works, so I'm not sure why its doing that. I'm guessing it is telling me that's a problem.
The third sensor has a pretty steady output voltage.
I'm not very familiar with OBD2 cars, but my understanding is that the upstream O2 sensor is expected to have voltage swings, and the downstream sensor is not.
What does it mean when that is reversed? Is it possible that the upstream O2 sensor's steady output is irrelevant? If so why would the downstream sensor have a wild swing? Faulty sensor, Cat, or both?
Typically when we get anything with a P0420, we advise the owner to first replace all the 02 sensors because oh yes a bad 02 can set that code. Run it a ew hundered miles, if the code comes back then it's cat replacement time.
On the question of Cali cats: it is my understanding that Cali cats are no different than 49 state except they have a different P/N because of the CARB standards. So what that means is that if a 49 state is installed it will work and won't set a CEL BUT! it won't pass Cali standards because the P/N doesn't match.
Knurled wrote:
You're missing the forest for the trees, here.
The reason why California felt the need to impose legislation regarding aftermarket cats, is a lot of aftermarket cats have so little precious metals in them that they are not effective at cleaning emissions, period. That $69 catalyst that ***co made is technically a cat but it doesn't work like one. Not well enough to actually do the job it is intended to do.
This isn't a California va. 49 state emissions standards thing. This is a California bothering to legislate aftermarket parts quality thing.
??? Not sure what your point is. I thought you were talking about how cars make PZEV, and I was answering that. OEMs use more metal for PZEV, which is how they make the emissions. Not just an air pump thing.
Both the EPA and CARB have requirements that all aftermarket emissions related parts meet specific standards. California's rules are tighter thanks to their tighter emissions rules.
In reply to HappyAndy:
Your understanding of how the system operates is correct. The first sensor in the stream is the control sensor, and the sensors behind it react to it. (there is some fuel trimming done via the 2nd sensor, but it's fine tuning for emissions)
One thing you may look into is if the front sensor is a WB sensor or not. The voltage output of that is much more steady. But it's also important to use a WB sensor to replace it. When you are using the torque app- can you record the short term fuel trims?
If the front sensor is correct, the fact that the second one is switching quickly would be an indication that the catalyst has failed.
Curmudgeon wrote:
Typically when we get anything with a P0420, we advise the owner to first replace all the 02 sensors because oh yes a bad 02 can set that code. Run it a ew hundered miles, if the code comes back then it's cat replacement time.
On the question of Cali cats: it is my understanding that Cali cats are no different than 49 state except they have a different P/N because of the CARB standards. So what that means is that if a 49 state is installed it will work and won't set a CEL BUT! it won't pass Cali standards because the P/N doesn't match.
Depends on the car. On this Altima, if it's the LEVII one, the cat is the same (based on how I read the cert results- the CARB-FED cert was done as one), but if it's the PZEV one, it's different. If the certification level is different, the cats are very likely to be different.
The Fed cat may appear to work, but it's not working the same. Which is the intention of the aftermarket part rules.
In reply to alfadriver: I'm 99% sure that the replacement O2 sensor is the correct type, I got the pn from Nissan's parts e-store, using the car's VIN.
I took that pn to NAPA, and their system identified that pn as an AFR sensor for a Cali spec Nissan. It was made by N-D, which is the OE supplier, and looked identical. It did not have the Nissan pn stamped on it, but something had been ground off in the same spot.
As for recording the short term fuel trims, I think I would need the pro version of torque app to do that, I do plan to upgrade eventually. It does have fuel trim monitoring listed as bank one sensor 1, bank one sensor 2, ect. I can display it in graph mode, and will have about 15 seconds worth on the display. To be honest, I'm not sure what the fuel trim numbers mean, or how to interpreted them.
In reply to HappyAndy:
Ok- so IF the front sensor is correct, and the system isn't flagging it as a problem, then I would thing that the system is operating correctly, and the cat efficiency code you are getting is real.
If the front sensor is dead, or wrong, it would be caught really quickly. The second and third sensor are reacting to how the catalyst are operating based on the first sensor's feedback. Some trimming is done, and some detecting is done. If that just gives you a catalyst code, it's probably just a broken catalyst.
For many years most of the NE states used California specs.
The window sticker on my '13 Fiesta says 50 state emissions.
