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Discussion Starter · #1 ·
So getting the catalytic converters off was a little easier than I thought it would be. My Murano has thrown P0430 and P0420 (which are both downstream codes bank 1 and 2) so I was expecting to see a shredded or clogged CAT on atleast one of them but they look pretty good.
I was thinking about just buying new sensors and converters but maybe something else is throwing the codes (spark plugs have never been changed 馃槼 but I'm definitely going to change them out before I put everything back together.
So just off of an eye test. Are these converters good or bad?? I couldn't get clear pics of the inside but they both look better than the outside.
Please help me before I just buy a bunch of new parts.....
53489
 

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Looks OK from the outside. Shake it. If you hear/feel rattling, the inside maybe damaged. If not, I would put it back in and try adding the anti fouler on the the downstream O2 sensor. It works great in eliminating the P0420,P0430 codes. I would try that first before purchasing any replacement. Those are not cheap to replace. Be sure to tighten the bolts properly to avoid vacuum leaks.
 

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the pics of the insides look very decent. and if the insides are better than the outsides, i'd say those are good to go back in. how many miles do you have on it? if it's well over 100k, than those spark plugs along with bad o2 sensors may be throwing a wrench in your soup. switch out the o2 sensor with oe type only. try new sparks & sensor before going the anti-fouler route if possible.
 

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I like to go the cheapest and easiest route first. In this case, put the anti fouler - $5-10. Drive the car and see what happens. If it does not fix it, change the O2 sensor. If that does not work, add in the anti fouler on the new sensor. If that does not work. Change the CAT. Make sure you erase the code after every repair.

My experience with P0420 code on my 99 odyssey, 2012-2015 I get the code occasionally and I can get it to disappear temporarily by putting the chevron Techron concentrate (1 0z / gal. ratio) in my gas tank. Later it won't work anymore. Tried the the anti fouler, skeptical at first, but after I added it on the original O2 sensor, it worked. Since 2016 to present the thing pass the NV smog yearly. With the original CAT @ 239K. No rain and no rust here in Vegas.
 

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First, what's the mileage?

I'm seeing about at least 30% flow reduction thru the honeycomb, at the surface.

IMO, after going thru the hassle of removing them, I'd be replacing them. All the tricks with the anti-fouler, running solvents, just delays the inevitable, and can cause further damage to the engine when the inside starts to deteriorate and crumble.

If you've replaced both/all the CO2 sensors with known good ones, and keep getting the errors, then the cats are clogged more then you can physically see.

This is only with the understanding that there are no other issues with fuel or air components, or another sensor being off which can effect the air/fuel ratio.

I replaced my cats at 130K after replacing all the co2 sensors. I bought them on eBay, one of the brands that Nissan uses for manufacturing, for less then $300 for both. I had the dealer install them, 3 hours labor, about $400.

Good luck.

Have a good day.
 

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After zooming in on the pics you posted, it does look like some of the honeycomb is partially plugged with residue. The outside of the converters won't tell you anything unless you find a hole or crack in the outer shell. In the Rust Belt, catalytic converters can get corroded badly after only a few years, but still work perfectly fine. If one or both of the converters are clogged then you should notice some engine performance problems (e.g. lack of power, RPMs will not rev above a certain point, etc.).

Nevertheless, it would be advisable to address any underlying problems that may be the root cause of them getting "clogged" before throwing new cats on the car or you may shortly be back in the same situation.

(spark plugs have never been changed 馃槼 but I'm definitely going to change them out before I put everything back together.
I find this problematic given that in this post you said your car had 147k miles on and that was 2 years ago! If the car has really gone this long without ever changing the spark plugs then that is outright neglect, IMO.
 
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Discussion Starter · #8 ·
After zooming in on the pics you posted, it does look like some of the honeycomb is partially plugged with residue. The outside of the converters won't tell you anything unless you find a hole or crack in the outer shell. In the Rust Belt, catalytic converters can get corroded badly after only a few years, but still work perfectly fine. If one or both of the converters are clogged then you should notice some engine performance problems (e.g. lack of power, RPMs will not rev above a certain point, etc.).

Nevertheless, it would be advisable to address any underlying problems that may be the root cause of them getting "clogged" before throwing new cats on the car or you may shortly be back in the same situation.



I find this problematic given that in this post you said your car had 147k miles on and that was 2 years ago! If the car has really gone this long without ever changing the spark plugs then that is outright neglect, IMO.
Interesting... I must have meant 137k ... because I only drove it till about August of that year. I've been running "guaranteed pass" etc thru it here and there before I finally broke down and took the cats out. Mechanics were saying they didn't want to touch it because they were scared of bolts breaking off. I broke one tiny bolt on the bank 2 heat shield doing it myself. I guess I'm better at getting rusted bolts off than they are lol.
So, yeah... the car hasn't been driven very much since that post. Still not an excuse for not changing the plugs which will be getting changed as soon as they arrive
How can you tell the honeycomb is clogged?? Are you sure it's not just shadows being cast??
Are you recommending new cats?? 馃槱
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Discussion Starter · #9 ·
the pics of the insides look very decent. and if the insides are better than the outsides, i'd say those are good to go back in. how many miles do you have on it? if it's well over 100k, than those spark plugs along with bad o2 sensors may be throwing a wrench in your soup. switch out the o2 sensor with oe type only. try new sparks & sensor before going the anti-fouler route if possible.
Miles are 139k nearly 140k... thanks for the insight!!!
 

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Discussion Starter · #10 ·
First, what's the mileage?

I'm seeing about at least 30% flow reduction thru the honeycomb, at the surface.

IMO, after going thru the hassle of removing them, I'd be replacing them. All the tricks with the anti-fouler, running solvents, just delays the inevitable, and can cause further damage to the engine when the inside starts to deteriorate and crumble.

If you've replaced both/all the CO2 sensors with known good ones, and keep getting the errors, then the cats are clogged more then you can physically see.

This is only with the understanding that there are no other issues with fuel or air components, or another sensor being off which can effect the air/fuel ratio.

I replaced my cats at 130K after replacing all the co2 sensors. I bought them on eBay, one of the brands that Nissan uses for manufacturing, for less then $300 for both. I had the dealer install them, 3 hours labor, about $400.

Good luck.

Have a good day.
Miles are 139k nearly 140k... what are you seeing showing its clogged is it that area that looks a little more worn than the rest of the honeycomb??
 

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Discussion Starter · #11 ·
Looks OK from the outside. Shake it. If you hear/feel rattling, the inside maybe damaged. If not, I would put it back in and try adding the anti fouler on the the downstream O2 sensor. It works great in eliminating the P0420,P0430 codes. I would try that first before purchasing any replacement. Those are not cheap to replace. Be sure to tighten the bolts properly to avoid vacuum leaks.
I gave them a shake today... no rattling coming from either. Thanks for the feedback too!! Really appreciate it!!
 

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How can you tell the honeycomb is clogged?? Are you sure it's not just shadows being cast??
Are you recommending new cats?? 馃槱
It may very well be the camera angle from the pictures. The color doesn't look bad (e.g. contamination). Bottom line--when a cat gets clogged, it literally gets clogged (i.e. exhaust flow becomes restricted) so that condition should produce some kind of driveability symptoms and I would think you would have said so if there were any. If you're concerned the converters may be clogged then shine a bright flashlight through the other end and you should be able to see it through the honeycomb if it's not clogged. You can also run clean water through one end to make sure it flows through freely (and perhaps compressed air if you have a compressor). Keep in mind that even if a cat isn't clogged, it doesn't mean the reactive substrate is performing as it's supposed to. Most people that get the P0420/P0430 codes don't notice anything out of the ordinary except the MIL is on.

I personally try to avoid replacing parts until I have ruled out all other possibilities. Frankly, if I had gotten those codes I wouldn't immediately take the cats off to inspect them. There are many other things that can cause the ECM to end up throwing those codes (e.g. vacuum leaks, exhaust leaks, faulty O2 sensors, intermittent misfires from worn spark plugs, etc etc)--if you look at the diagnostic scheme in the service manual, the last thing out of a very long list of things to look at are the catalytic converters themselves. But, you have everything apart now so I guess the question is how far do you want to go with this? If you have the cash, you can replace the cats, O2 sensors, and spark plugs and likely resolve the problem. But, was all that necessary? Probably not (although the plugs really do need to be changed--140k miles? Come on man! :) ). Alternatively, you can just change the spark plugs with something high quality like Denso or NGK Iridiums for now and put everything back together with new gaskets making sure that you don't have any vacuum leaks (or exhaust leaks), clear the codes, and see if they come back. If they come back, then you can reasonably rule out the plugs and turn your attention to something else that might be causing the problem.

BTW, just in case you can find the service manual for your car here: https://www.nicoclub.com/nissan-service-manuals
 

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Discussion Starter · #13 ·
It may very well be the camera angle from the pictures. The color doesn't look bad (e.g. contamination). Bottom line--when a cat gets clogged, it literally gets clogged (i.e. exhaust flow becomes restricted) so that condition should produce some kind of driveability symptoms and I would think you would have said so if there were any. If you're concerned the converters may be clogged then shine a bright flashlight through the other end and you should be able to see it through the honeycomb if it's not clogged. You can also run clean water through one end to make sure it flows through freely (and perhaps compressed air if you have a compressor). Keep in mind that even if a cat isn't clogged, it doesn't mean the reactive substrate is performing as it's supposed to. Most people that get the P0420/P0430 codes don't notice anything out of the ordinary except the MIL is on.

I personally try to avoid replacing parts until I have ruled out all other possibilities. Frankly, if I had gotten those codes I wouldn't immediately take the cats off to inspect them. There are many other things that can cause the ECM to end up throwing those codes (e.g. vacuum leaks, exhaust leaks, faulty O2 sensors, intermittent misfires from worn spark plugs, etc etc)--if you look at the diagnostic scheme in the service manual, the last thing out of a very long list of things to look at are the catalytic converters themselves. But, you have everything apart now so I guess the question is how far do you want to go with this? If you have the cash, you can replace the cats, O2 sensors, and spark plugs and likely resolve the problem. But, was all that necessary? Probably not (although the plugs really do need to be changed--140k miles? Come on man! :) ). Alternatively, you can just change the spark plugs with something high quality like Denso or NGK Iridiums for now and put everything back together with new gaskets making sure that you don't have any vacuum leaks (or exhaust leaks), clear the codes, and see if they come back. If they come back, then you can reasonably rule out the plugs and turn your attention to something else that might be causing the problem.

BTW, just in case you can find the service manual for your car here: https://www.nicoclub.com/nissan-service-manuals
Super thanks for the service manual!!! And yes I get what you're saying about just throwing the whole kitchen sink at a repair instead of ruling out possibilities. I ran water thru the honeycomb and it passed thru with no obstruction. So I'm going to change all 4 sensors (no reason not to while I have everything apart) and DEFINITELY THE SPARK PLUGS 馃槄馃槀. I'll put it all back together and see if I can catch a break and also keep everyone posted just for future reference if anyone else finds this thread in the future.
Should have it back together in about a week depending on when everything arrives.
 

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I know cats are gonna be expensive right now. I've heared of resting the cats in buckets of lacquer thinner for a few days to help clean clogs out. I hear this only works if only slightly clogged and/or barely. I've also hear of putting some lacquer thinner in the gas tank and running the car at 2000 rpm for a couple hours with the cats still installed, but I think the jury is still out on whether that truly works or not. Idk good luck
 

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I know cats are gonna be expensive right now. I've heared of resting the cats in buckets of lacquer thinner for a few days to help clean clogs out. I hear this only works if only slightly clogged and/or barely. I've also hear of putting some lacquer thinner in the gas tank and running the car at 2000 rpm for a couple hours with the cats still installed, but I think the jury is still out on whether that truly works or not. Idk good luck
I would be a loud NO vote on adding lacquer thinner to the fuel!!! Holy cow, aren't converters cheaper than engines???
 

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I would be a loud NO vote on adding lacquer thinner to the fuel!!! Holy cow, aren't converters cheaper than engines???
I know, sounds crazy right? I would be more apt to resting the cats in a bucket than running through the engine, however there are a lot of testimonials out there from diyers to mechanics with 50+years of experience. One of the more reputable mechanics I've seen "Scotty Kilmer" says to try it. Actually I think he references laundry detergent for the bucket method.

 

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Yeah I guess cheap aftermarket catalytic converters go for cheap on ebay. Who would of thought? I think the op was asking a question about whether or not he should throw parts at it. I dont think he/she was looking for a link to ebay, but I'm not a super moderator.
 

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Yeah I guess cheap aftermarket catalytic converters go for cheap on ebay. Who would of thought? I think the op was asking a question about whether or not he should throw parts at it. I dont think he/she was looking for a link to ebay, but I'm not a super moderator.
So helping someone out with alternatives shouldn't be done?

And what the heck does being a 'super moderator" have to do with anything in this discussion?

Have a good day.
 

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$275 for all three cats + hardware is a steal. Now, how well they end up fitting might be another story :p.

Below is the MSDS for a popular brand of lacquer thinner (Klean Strip) and one thing that stands out is the major ingredient is acetone (<= 50%) and even though it would get diluted in a tank of gasoline, I would be reticent to run that in my fuel system. There is a popular product marketed for cleaning cats (Cataclean) that also has acetone although at much lower levels (20%) and the major ingredient in that is xylene, which is already present in gasoline blends to some degree. I guess you could try something like this before you start taking the exhaust apart and only if you have reason to believe that the catalytic converters are actually contaminated (e.g. engine burning oil, blown head gasket, or whatever) as opposed to worn. But, as far as soaking them for days in lacquer thinner or laundry detergent--unless you're hard for cash and your time is not worth very much, I don't see why someone would want to put themselves through that, IMO. If it doesn't work (more than likely) then you have to replace them anyway, which means doing the whole job twice. The OP said getting the cats off was "a little easier than I thought it would be"...He didn't say it was "easy".

And again, before you condemn the cats you should try to rule out all other possibilities.

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