2012 Pathy - p0430 bad cat? or is it?

[butchbr73]

New to this board, but long time Nissan owner. This is our 4th Pathfinder over the years.. bought new in 2012, now has 83k miles. Dropped a K&N drop in filter in it at some point a few years back, only "mod" done. Right at 83k miles, CEL on and brought to dealer, p0430 b2... dealer says bad cat - $1,150+ tax for repair. I choked and picked the vehicle up. Calling Nissan warranty to see how lenient they'll be... since catalytic converters have 80k warranty. I've owned too many other Nissans to count over the years, and currently our other vehicle is an Armada.

Now the interesting part, talking with other folks (other third party shops that are much cheaper to repair cats).. cat's don't just go bad, something causes them to go bad. Now I'm thinking back and have been noticing for a few months, maybe longer but wife mostly drives it so I'm not in it much, the car had a rough idle. Noticed weeks ago from the outside that also the exhaust note was sort of popping in idle, not a smooth idle... hmm... as well, noticed a faint smell of what one might call rotten eggs but can't really place the smell, not your typical exhaust smell. Well, doing a bit of research on what would cause a cat to go bad.. engine running lean or rich could, dropping gas into the exhaust, etc. I realized the K&N filter would push more air into the engine, thereby causing the car to think it needs to add more fuel to counteract... could that be the root cause of the issues? Also one of the guys at a third party shop checked the cats with a temp gun and he said the rear ones are bad, guess you can tell by the temperatures in and out..? If the temperature in/out is too hot, its not oxidizing all the exhaust. Well, also realize a lean running engine would run hot and the exhaust would be hot, could that provide sort of a false positive for a bad cat?

Last night, I went and bought your typical Purolator air filter and put that back in and pulled the K&N out. This could all be in my mind, but I started the car and let it run for a minute and I swear the rough idle "went away" and is now much smoother idle. Driving around for a few minutes noticed a little smoother... as well, when I pulled back in and let it idle, the exhaust note is now much smoother... and that faint smell is gone.

Now, Nissan had turned off the CEL when we brought it in for a diagnosis last week.. and it has not come back on yet. I've had numerous K&N's over the years in various Nissans and never had an issue before... I'm going to run it a bit with the OEM paper filter to see how she does over time and see if the light happens to come back on. Has anyone experienced or heard of this sort of issue before between a stock filter and K&N filter?
Did I kill that cats already if by chance the engine was running lean for some time? Any Thoughts?

[MisterH]

CC's are destroyed by unburned fuel (running too rich). That is a puzzling scenario you described. Hope your CEL stays off.

[rgk]

Yeah, it's an interesting scenario, but not one any of us are going to solve for you. The way I see it, you have one of two choices: wait to see if the CEL comes back on, or get a scan tool and check your O2 sensor voltages. My P0420 throws a pending code within the first two to five drive cycles.

Are you losing any oil? Cats are also fouled with burning oil.

[butchbr73]

thanks rgk. was last Friday Nissan flipped the light off, no CEL light yet. Its been driven about 400-500 miles since then (multiple cycles from short city to multiple 100 mile highway drives) with no issues since replacing the K&N a few days ago, still appears to be running much smoother. I'm not sure if my original question was necessarily asking for someone to solve (although that would never hurt and would never turn down help!), maybe I'm more curious if anyone has heard or had seen similar issues with K&N's before? I may have already solved it - fingers crossed - kinda crazy if the truck is that finicky..
Does not appear to be burning oil as far as I can tell. I do not currently have a scan tool, but will try to get my hands on one to see if I can get the O2 sensors... if so, I'll update. Since its almost time to change plugs, was also thinking will do that as well.. cross another item off the list as possible cause of misfires, etc.

[butchbr73]

well now may never know the real answer but just got a call from local Nissan dealership, Nissan corp. has authorized them to replace the cat under warranty. Still confused on the whole k&n filter vs. oem filter and how the car now runs but we'll see if after the replacement we run into any other issues. k&n filter will be shelved permanently for this vehicle.

[heavy hitter]

So i realize this is a super old thread....but this issue seems to be a common issue among r50 motors. Anything that enhances airflow such as aftermarket air intakes and especially aftermarket high flow cats seems to throw codes for catalytic convertors, and bank 1 o2 sensor issues. A pretty simple fix that ive seen work lots of times is an 02 sensor spacer on the passenger side secondary sensor. it gets the sensor out of the stream of exhaust and stops the code in a lot of cases. This is not specifically legal in states requiring emissions testing....but just throwing it out there as an option.