P0420: Do I need a new catalytic converter?

[KingCarGuyZ]

Ok, so about 3-5 months ago when I first got the Jeep, she had a emissions code problem, no biggy, went through a little bit of a fight to get the right NTK sensors (I installed Bosch ones first) and all was good, the code was gone. Then I had a battle with the TPS sensor. Got that sorted out and now I. Can’t get the P0420 (bank 1cat below efficiency) to go away. The Jeep has 4 NTK 02 sensors (upstream and down stream) that are all 3-5 months old. When I replaced the 02’s I used a endoscope to look at the cats and they seemed fine ( see photo ). My question is do I throw another sensor at it? Or just bite the big one and buy a cat? Something else? Keep in mind this is a persistent code that has been cleared at least 5 times and still comes back. Also she’s a 2001 4.0 5spd with 256,xxx miles if that helps.

 

[Goatman]

Can you swap to the other side and see if the problem switch side too? Then you know it's a bad sensor. If the problem stays same side then you know it isn't the sensor.

 

[Steel City 06]

Has the vehicle been driven hard since the other issues? If not, carbon and other deposits can build up on the catalyst and reduce its efficiency. If it hasn't been run hard, a long Italian tuneup might be a good way to try and clean it out. The idea would be to get the catalytic converters as hot as possible. If you can find a freeway that allows 75+ and do a lot of hard acceleration or fast hill climbs, that should burn up any deposits.

If that doesn't do anything, it may be worth replacing the catalytic converters. I replaced mine with a bolt in Magnaflow unit. It wasn't cheap but it fit perfectly and has given me zero issues.

 

[KingCarGuyZ]

I just finished a country road trip yesterday where I was running 70-80
And I do my fare share of second gear pulls. But other than that she gets fairly mild driving.

I believe I can swap the downstream bank 1 with the upstream bank 2 or something (it has to do with the length of the tail/plug.)

 

[Steel City 06]

I just finished a country road trip yesterday where I was running 70-80
And I do my fare share of second gear pulls. But other than that she gets fairly mild driving.

Then carbon is probably not the issue. Buildup is often seen in cars that only do short, low speed trips, like to the grocery store and back. It takes a certain amount of heat to get the catalytic converter to light off, but once it does so, it should get hot enough to cook out any deposits.

 

[KingCarGuyZ]

I guess I’ll try and swap the 02’s and see if that does anything.

assuming I do need a CAT do I bother with the CARB rated one? Or is the 49 state legal good enough? I live in TX so it’s not a concern beyond what the engine wants.

 

[Steel City 06]

Under the hood, there should be a big sticker that has the emissions information. It will either say something like California emissions or federal emissions.

If it has a sticker for California emissions, you will need a catalytic converter compatible with that emissions system. It doesn't necessarily need to be a CA-legal converter, but it does need to be compatible.

Vehicles with CA emissions software have a higher threshold of emissions standards, and require more rare metals in the catalytic converters to achieve the threshold necessary to turn off the CEL. Vehicles with EPA minimum software can get away with heavy metal catalytic converters, which aren't as efficient.

California requires a very specific sizing for catalytic converters, so not only do they need the higher rare metal load, they need to be sized differently than most aftermarket manufacturers do. Vehicles with CA emissions outside of California are not subject to these requirements.

Magnaflow makes all three kinds of catalytic converters. The rare metal converters will work fine in a vehicle that only requires heavy metal converters, but not the other way around. The rare metal converters are more efficient at converting pollutants into inert gases.

 

[KingCarGuyZ]

So I have a new to me Fed emissions CAT coming. (Thanks @Pullski ) should I throw a whole new set of NTK sensors at It as well, while I have the CAT out? Or just swap the old ones over? (Whole set of NTK’s from rockauto is about 100 bucks)

 

[Aluminum Falcon]

I believe the Bosch sensors have been deemed no bueno.

 

[Kaptainkid1]

Can a Catalytic converter last 18 years and 170,000 miles? My Jeep is running good and passes smog no problem in CA. No check engine lights and I've seen a ton videos and threads where cats on Jeep TJ fail under 100k. These Jeeps are clogged and throwing codes.
Mine is a used Jeep so who knows if the cats we're replaced at a 100k and I have another 30k left on a 2nd set maybe. I wanted to know, do I need to worry and maybe replaceing the cats are in my Jeep's near future?

 

[KingCarGuyZ]

Tbh I’m on factory CAT’s and near 256,000 and they just started acting up, I haven’t heard of CAT’s in Jeeps being prone to failure, And many of the other cars I work on are well into 200,000’s and still on factory cats with no sign of needing a replacement. In summary your cats “shouldn’t” go bad, in less another problem breaks them. (Like a dud 02 that caused you to run rich/lean for to long)

 

[KingCarGuyZ]

I believe the Bosch sensors have been deemed no bueno.

Yeah, I made the mistake of using BOSCH first. They are duds and didint work, but the NTK’s Solved my problem until I had to reset the computer again.

 

[Steel City 06]

Mine self-destructed at 54,000 miles. Had a nasty period of misfires and limp mode that I couldn't figure out until it suddenly went away. Turned out one of the pre-cats self-gutted and plugged the 3rd cat.

 

[Pullski]

So I have a new to me Fed emissions CAT coming. (Thanks @Pullski ) should I throw a whole new set of NTK sensors at It as well, while I have the CAT out? Or just swap the old ones over? (Whole set of NTK’s from rockauto is about 100 bucks)

You got it! I will throw in my sensors as well because my Jeep wasn’t throwing any codes. I hope it works out for ya! My Jeep passed emissions in TX before it was shipped out here so you should be just fine

 

[Lou]

In my 9 years experience working on cars and trucks, I have never seen a p0420 or p0430 be caused by anything but a cat.

 

[Kaptainkid1]

Here is video of a guy buying for California Compliant Catalytic converter from Walker and honestly it seems the catalytic is made with bad bend, cheap welds and isn't aligned properly on the O2 sensor. Doesn't anyone have a better company for California Compliant Catalytic?

 

[Pullski]

Here is video of guy buying for California Compliant Catalytic converter from Walker and honestly it seems the catalytic is made with bad bend, cheap welds and isn't aligned properly on the O2 sensor. Doesn't anyone have a better company for California Compliant Catalytic?

I think either MOPAR or the Magnaflow are the best ways to go in terms of quality. It’s probably worth the extra dough for the build quality. @KingCarGuyZ the cat is very roughly boxed up. I am planning on going tomorrow or Saturday to get it mailed out to ya!

 

[Steel City 06]

I bought the Magnaflow cats for California emissions vehicles outside of California, and am pleased with it. It fit perfectly and gave me zero issues. They also have ones that are compliant for vehicles inside California.

 

[KingCarGuyZ]

Magnaflows are really nice I’m told, but there really expensive.

 

[Goatman]

I have been less than pleased with any Walker products in my years of experience. Unfortunately they are often the only brand available for many older vehicles. They do tend to stand by their warentee, but often I've had pipes rust and crack in less than 2 years. I am up in the Salt zone in NY so others in better climates may have different opinion.