Catalytic converter question for the automotive guys

Wrench978

Wrench978

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Wrench978
I recently bought a 2012 Nissan Frontier and the Catalytic converter has failed (per the dealer). It is a CARB (california) emissions truck, but it is not owned or operated in a state that requires the more stringent emission standard. its not under warranty so Im looking at doing it myself. the local muffler shop said that if I don't put a CARB cat in the truck that I will end up with issues in the near future. the price difference is pretty significant for me though

My question is, aside from the legality of it, will putting a standard EPA catalytic converter cause me any issues? the emission testing around here is a joke... "Your car doesn't pass? let me stick the probe in another car and just throw me a couple extra bucks"

Im concerned with doing long term damage to my engine. Should I be?
 
Wrench978 said:
will putting a standard EPA catalytic converter cause me any issues?
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Wrench978 said:
Im concerned with doing long term damage to my engine.
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Issues... yes. But not with the tests. The emmission side of computer may have some issues. Just went through same on 2003 Tribute. All 3 converters falling apart. OEM = $3600+. Muffler shop = $600 a piece to recore. Online, rockauto I think, and installed by a friend... $650 total. And no more service engine light to boot.
 
Generally it's something other than the catalytic converter. That said, it could be still be under warranty, I think the fed warranty is 8 years 80,000 miles. If the converter still has the honey comb in it it might be something else. Most smog tests now don't use the probe, they just check the obd system which rats you out. What codes are you getting?
 
PaulS said:
Generally it's something other than the catalytic converter.
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Correct.

Usually it is something else engine related that goes haywire, then ruins the catalytic converters as a symptom. The muffler shop should have told you that.

It is well worth it to find out what is wrong before replacing the cats twice.
 
Zeldman said:
Correct.

Usually it is something else engine related that goes haywire, then ruins the catalytic converters as a symptom. The muffler shop should have told you that.

It is well worth it to find out what is wrong before replacing the cats twice.
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I would still like to know the test they used. There are OBD tests that point to failed cats because temps or O2 sensors don't change the way they should, but in reality there is air getting into the system when it shouldn't screwing up the test. We need more details. It sucks to change a catalytic converter and have it fail again or worse not fix the problem.
 
Need new Cats on my 2003 ML320. OEM $$$$ I'm going for something after market, a first on my vehicles. With 225,000 and 15 years old, I think the ML will survive.
 
The non-carb cat may have a downstream O2 sensor mounted in a different place (or not at all - not that likely). Otherwise differences would be total volume or the precious metal loading or sometimes the catalyst will be located closer to the engine. I wouldn't get real worried about having the non-carb cat on it.
Now, how did they determine that the catalyst is bad?
Diagnostic code? The OBD-II diagnostic for the catalyst efficiency is one of the least reliable monitors out there. I wouldn't get excited about that code either. Sometimes an Resistor / Capacitor filter in the O2 sensor line will cure the code - search for "MIL Eliminator" - they are popular with the Mustang crowd...
Did it fail the idle emission test? The correlation between the actual catalyst efficiency and the idle emission test results are also weak. Warm it up better before you get it tested.
Vacuum leaks? Misfires? Low fuel pressure? Things to check b4 you replace a cat.
 
GMascelli said:
Need new Cats on my 2003 ML320. OEM $$$$ I'm going for something after market, a first on my vehicles. With 225,000 and 15 years old, I think the ML will survive.
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Same deal as above Gary, unless you know the ceramic is gone be careful. That said, I had a cat fail on my 2003 s500, at about 75,000 miles, they tested and replaced it under warranty. The car sounded like it was popping popcorn.
 
Capt. Geoffrey Thorpe said:
The non-carb cat may have a downstream O2 sensor mounted in a different place (or not at all - not that likely). Otherwise differences would be total volume or the precious metal loading or sometimes the catalyst will be located closer to the engine. I wouldn't get real worried about having the non-carb cat on it.
Now, how did they determine that the catalyst is bad?
Diagnostic code? The OBD-II diagnostic for the catalyst efficiency is one of the least reliable monitors out there. I wouldn't get excited about that code either. Sometimes an Resistor / Capacitor filter in the O2 sensor line will cure the code - search for "MIL Eliminator" - they are popular with the Mustang crowd...
Did it fail the idle emission test? The correlation between the actual catalyst efficiency and the idle emission test results are also weak. Warm it up better before you get it tested.
Vacuum leaks? Misfires? Low fuel pressure? Things to check b4 you replace a cat.
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The California obd test is pretty sensitive to foil the hacks. There generally is an upstream and down stream O2 sensor. Every so often the O2 level is tweeked and the down stream sensor needs to detect the change or it fails. That's the one that got me, dealer kept saying new cat, so finally I did it myself. Guess what, didn't fix it. I had asked them 10 times to replace the PVC valve they kept saying that couldn't possibly be the cause or they didn't have one in stock. After I replaced the cats I got ****ed, had to buy a pvc valve on amazon because no one had one in stock. Replaced it, then after about 5 miles the MIL went out. Go figure, it was letting air in when it shouldn't have causing it to flunk the test.
 
Agreed with the others - what makes the dealer think it’s the catalytic converter?

Have someone pull O2 values from the OBD2 port. If they’re pretty different, you can try to first replace the O2 sensors. NAPA has them at reasonable prices. In my case, the parts NAPA had were Bosch and identical to the more expensive Ford parts. CARB makes things rough here because they measure O2 sensor values before and after the catalytic converter. If you can swap the ECU with a non-CARB version, you can potentially use a non-CARB catalytic converter exhaust.
 
ok, here is the full story. Check engine light came on, engine was misfiring. Nissan dealer said bad ignition coil, covered under the extended warranty that the truck had. they replaced it, but said the check engine light was still on, and it was throwing a code for another cylinder now. I drove the truck for a couple days until they had the coil in stock, and they replaced it. drove the truck for a couple more days, engine light came on for a 3rd time and they said it was a 3rd coil. I asked them to try to get the 4th coil covered but no such luck. I drove it for a few days with a misfire until I could get it to them, which they said was a bad idea, but I didn't have a choice. so the CEL came on a 4th time and they said it was throwing a P0240 code and the cat was shot. this wasn't covered under warranty, and Im cheap, so I brought it to the muffler shop to see if they could weld in a universal cat. Thats when the I can get some numbers later.
 
My car is catless and runs better than it did when it was stock. You'd have to get it tuned, but that's not a big deal.

Another alternative is to ask @AggieMike88 if his yard has a downpipe for a Frontier.
 
PaulS said:
The California obd test is pretty sensitive to foil the hacks. There generally is an upstream and down stream O2 sensor. Every so often the O2 level is tweeked and the down stream sensor needs to detect the change or it fails.
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If the downstream sensor doesn't switch fast enough, it will flag the downstream sensor as bad. If it switches too much or too fast (relative to the upstream) then they claim the cat is bad. More or less... It's been a few years since I had the misfortune to be working on those diagnostics.

Wrench978 said:
I drove it for a few days with a misfire until I could get it to them, which they said was a bad idea,
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OK, yea, you didn't do your cats no good. Any fuel from misfiring cylinders ends up burning in the cat and overheats it. The computer should shut down the fuel to the offending cylinder to minimize damage, but...
The question is - was it really the coils going bad? Or something else causing misfire and the tech shotgunning parts?
 
Capt. Geoffrey Thorpe said:
The question is - was it really the coils going bad? Or something else causing misfire and the tech shotgunning parts?
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after they replaced the 3rd coil it has been running fine, minus the check engine light for cat efficiency. they actually showed me a spot on one of the coils that showed "proof" of the misfire.
 
AggieMike88 said:
Sorry, I don't. Not enough activity on the part type to bother with for any car or truck.
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thats fine. I found a good price on the regular EPA cat. just wanted to know if Im gonna screw something up on my truck if I don't use the California cat
 
Data point: bought a low mileage for it’s age Ford Expedition w/ 5.4 really damn cheap in Sacramento because it needed cats ($2k job even for aftermarket stuff in CA). It really did need cats, clogged to the extent that it misfired significantly on the drive home when I presssed on the go fast pedal. Got it to a no emissions testing area, put non-CARB cats on it ($300 on amazon). Two years and 10k miles, no problems, no codes.
 
catmandu said:
Data point: bought a low mileage for it’s age Ford Expedition w/ 5.4 really damn cheap in Sacramento because it needed cats ($2k job even for aftermarket stuff in CA). It really did need cats, clogged to the extent that it misfired significantly on the drive home when I presssed on the go fast pedal. Got it to a no emissions testing area, put non-CARB cats on it ($300 on amazon). Two years and 10k miles, no problems, no codes.
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thats exactly what I was hoping to hear. I have no problem replacing the cat. I drove it with the misfire knowing I might be doing damage but didn't have a choice. I would just rather spend 200 bucks for the non-CARB cat than 500-600 for a CARB compliant version.
 
Move to Nebraska, then cut the damn thing off and weld a pipe in its place. Put a piece of tape over the check engline light and you’re better than new.

Shop down the street will do the job for $100, cash, no receipt.
 
jesse said:
Move to Nebraska, then cut the damn thing off and weld a pipe in its place. Put a piece of tape over the check engline light and you’re better than new.

Shop down the street will do the job for $100, cash, no receipt.
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I thought about doing something similar here in Puerto Rico, but the Cat is part of the exhaust manifold. Cutting it out would be pretty tricky. and I like having a functioning CEL. I could put an O2 spacer in that might help that.
 
Before replacing the cat have a shop do a 3 step fuel injection cleaning. What ever they call it may be different but it’s all the same. It’s an iv like. drip in the intake manifold and it’s suppose to clean it out. What it does very well though is get the converter really really hot and cleans it out. I assuming you have either a p0420 or P0430 code, depending which bank. I suggest this to every customer who has a failing cat that isn’t phsyically damaged or leaking and it clears maybe 75% of converters.

Second putting a non carb converter on a Nissan that is carb required will through a cel light. They are very picky on the emmissions stuff. Ford Expedition not so much.
 
How hard is it to just delete all that crap and reprogram the ECM?

That’s what I did to my truck. Works much better now. Get way better gas mileage too.
 
Criitter7 said:
Before replacing the cat have a shop do a 3 step fuel injection cleaning. What ever they call it may be different but it’s all the same. It’s an iv like. drip in the intake manifold and it’s suppose to clean it out. What it does very well though is get the converter really really hot and cleans it out. I assuming you have either a p0420 or P0430 code, depending which bank. I suggest this to every customer who has a failing cat that isn’t phsyically damaged or leaking and it clears maybe 75% of converters.

Second putting a non carb converter on a Nissan that is carb required will through a cel light. They are very picky on the emmissions stuff. Ford Expedition not so much.
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Thanks. Ill look into that.


Tarheelpilot said:
How hard is it to just delete all that crap and reprogram the ECM?

That’s what I did to my truck. Works much better now. Get way better gas mileage too.
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Im looking into that option. Ive been reading about people just removing the honeycomb and putting a non-fouler on the rear O2 sensor and it works... Thats a cheap experiment that I could try...
 
I can't imagine that there is any difference in the CARB vs non-CARB cat that would throw an error code. I'd think a 2012 model vehicle would be covered under warranty unless you're past the 80,000 mile mark for federal emissions devices. I'd have them put the non-Carb unit in and take my chances.
 
I had this issue with my previous car. My cat went out and Subaru said they could replace it with a standard one. Well a week later they called back and said they only stocked CARB versions now days and it was an extra $1500. :confused:
 
I’ve never replaced a catalytic converter, but I have replaced a few of the downstream O2 sensors which tell the computer the cats are working.

Also if you don’t care or are nearly curious google MIL eliminator.
 
The engine doesn't care whether or not it has catalytic converters installed, you won't harm it either way.

Personally I'd go with the cheap option if I was going to do that.
 
thanks for the input everyone. Im going to try removing the honeycomb and putting a non-fouler on the rear O2 sensor this weekend. If that doesn't work, Ill get the non-CARB cat for 200+ shipping.
 
Wrench978 said:
thanks for the input everyone. Im going to try removing the honeycomb and putting a non-fouler on the rear O2 sensor this weekend. If that doesn't work, Ill get the non-CARB cat for 200+ shipping.
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Won’t work, Nissan uses wide band o2 sensors, the the computer is to sensitive to be fooled by a fake senser. It will throw a light
 
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