Recommendations for Catalytic Converter

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Nick1994

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This is for my 1996 Jeep Cherokee 4.0L. After years of off-roading the catalytic converter has hit quite a few rocks and it seems it might be broken a bit inside causing this exhaust rattle. Sometimes it rattles, sometimes it doesn't. Only does it at idle though. It's obviously coming from the catalytic converter, muffler seems fine. Jeep is quiet when it isn't rattling.

So what recommendations do you guys have for a cat and maybe a muffler? There's a local exhaust shop that'll weld in new stuff for cheap, they welded in a cat my brother brought in for his truck a few months ago for $40. Catalytic converter has an oxygen sensor screwed into the back so the new one will need that port.

I'm considering replacing the muffler as well. I don't want it loud, I want it very quiet on the highway with perhaps a little sound when I'm on the throttle. Not important though. Also don't want to spend a huge amount on it. Might just keep the original muffler though, still undecided.

Maybe get a catalytic converter with better flow for better performance? It's pretty quick as it is, but I don't really know anything about exhaust stuff so I'm open to recommendations.
 
I didn't know you could pick and choose in Arizona. In California, the number on the catalytic converter has to match the EFN number on the under hood sticker and that's it. The only aftermarket company I found that has one to match is Magnaflow. None of the other aftermarket companies want to get involved with California stuff.
 
Originally Posted By: Trav
Do you have an emission test?
The only emissions we have here is 1996 and newer vehicles get scanned for check engine lights and a gas cap pressure test, that's it. 1995 and older vehicles get run on the rollers with the exhaust sniffed. As long as I don't set a CEL I'm good.
 
Trav might have a point there if you want to go the cheap route.

Yoy might get away with it with your older style ecu. Tried that route on my car too but an extender on the rear oxygen sensor messes with the A/F ratio on the modern ecu's. The older ones only use the post cat o2 sensor for cat-funtionality checks, the newer ones also check the pre cat o2 sensor with it and it will make your car set a different fuel trim. At least it does on TFSI engines.
 
If you have room for a larger physical normal sound level muffler, I'd go that route. My brother used that trick building a street sleeper 1970
Buick Skylark.
 
96 jeeps were recalled for not having the ecm programmed to monitor cat efficiency. You can get it warrantied, but they are going to reflash the ecm at the same time to make it begin monitoring cat efficiency. I was a jeep tech when the recall came out. If you go this route you'll get a free cat plus install and it'll be a quality part.

If you want to go aftermarket I've had good luck with bosal premium packed converters.
 
That's kind of cool. My 96 XJ has that recall open. Maybe I should take care of it.

The OE one would be the highest flowing. Otherwise, the more states it's legal in, the better flowing it will be.

I got a Walker Quiet flow muffler for my XJ. No idea what was on there before, maybe it was the OE one but it was rotted out. I like the Walker one, really only hear the exhaust when you floor it, at cruise it's pretty quiet. I wanted to get as close to the OE one as possible.
 
Originally Posted By: Tommiee
Trav might have a point there if you want to go the cheap route.

Yoy might get away with it with your older style ecu. Tried that route on my car too but an extender on the rear oxygen sensor messes with the A/F ratio on the modern ecu's. The older ones only use the post cat o2 sensor for cat-funtionality checks, the newer ones also check the pre cat o2 sensor with it and it will make your car set a different fuel trim. At least it does on TFSI engines.


+1 Many newer cars use the rear O2 to fine tune fuel trims. US manufacturers are not giving the rear O2 much authority (1% or less) but Toyota is 2% and some Euro cars from what I have read up to 3% (not verified info). This Jeep will have no trouble.
The value of cats on older vehicles like this one has been tested and debated for over 30 years, no doubt the newer models really do a good a good job of cleaning the the exhaust gasses but the older ones in some dyno test actually made some values like NOx worse by reducing the engines efficiency, increased combustion chamber temperatures and increased fuel consumption so environmental impact running without will probably be a wash or close to it on this car.
 
Before replacing I would investigate a little further and make sure it's not something else. Could be a loose heat shield or muffler clamp. With a cold engine/exhaust and engine running.... I'd get under there with a glove in hand and grab ahold of the Cat, Heat shield and Muffler and see if the rattle goes away.
 
Originally Posted By: t1snwrbrdr12
96 jeeps were recalled for not having the ecm programmed to monitor cat efficiency. You can get it warrantied, but they are going to reflash the ecm at the same time to make it begin monitoring cat efficiency. I was a jeep tech when the recall came out. If you go this route you'll get a free cat plus install and it'll be a quality part.

If you want to go aftermarket I've had good luck with bosal premium packed converters.


I'd go this route if it is viable...

I've found that on real dyno tests, the one size weld in converters work just marginally better than an OE one at the end of life. A real OE one will work MUCH better.
 
Quote:
+1 Many newer cars use the rear O2 to fine tune fuel trims. US manufacturers are not giving the rear O2 much authority (1% or less) but Toyota is 2% and some Euro cars from what I have read up to 3% (not verified info).
Is there a link to verify this information?
 
I've read about the recall but was under the assumption that they wouldn't replace the car if it isn't under the emissions warranty? Not sure. It's worded a little weird. Not sure that they'd replace it, it's got lots of dents in it.

Originally Posted By: Trav
Is the cat body still okay? If it is just empty it and run a extender on the rear O2 to keep the thing from setting a cat code.
My brother has a 91 Cherokee and he emptied out the cat last year and it's ridiculously loud.
 
Some cars it hardly makes a difference but others do get louder or resonate, just install a pipe with a bung in its place, my point was just to eliminate the cat if you want to.
 
Originally Posted By: Nick1994
I've read about the recall but was under the assumption that they wouldn't replace the car if it isn't under the emissions warranty? Not sure. It's worded a little weird. Not sure that they'd replace it, it's got lots of dents in it.

Originally Posted By: Trav
Is the cat body still okay? If it is just empty it and run a extender on the rear O2 to keep the thing from setting a cat code.
My brother has a 91 Cherokee and he emptied out the cat last year and it's ridiculously loud.


A recall shouldn't matter whether you are in any warranty or not. It was the manufacturers fault so of the vehicle is still in use it should be fixed regardless. I fixed mine at around 180-200k miles when the recall came out.

For the mechanic the recall stated something along the lines of "if it rattles, replace it immediately. If not, replace the cat if the 420 efficiency code comes back" but it had to set a fault within a specified time after the ecm was Reflashed. The ecm is to be reflashed regardless of what they do or don't do with the cat.
 
Last edited:
Originally Posted By: JHZR2
Originally Posted By: t1snwrbrdr12
96 jeeps were recalled for not having the ecm programmed to monitor cat efficiency. You can get it warrantied, but they are going to reflash the ecm at the same time to make it begin monitoring cat efficiency. I was a jeep tech when the recall came out. If you go this route you'll get a free cat plus install and it'll be a quality part.

If you want to go aftermarket I've had good luck with bosal premium packed converters.


I'd go this route if it is viable...

I've found that on real dyno tests, the one size weld in converters work just marginally better than an OE one at the end of life. A real OE one will work MUCH better.


I've actually got two '96 Jeep Cherokees, both with the 4.0 engine.
About a year ago, I walked into the Jeep dealership with my VIN numbers. One Jeep with the automatic transmission did NOT have an open recall. The other Jeep, with the manual transmission, had an open recall for the converter. The shop foreman told me that they would do a visual inspection on my Jeep to determine if a new catalytic converter would be needed. AT THEIR DISCRETION, they would decide if my Jeep would qualify for a new converter. They would also do an ECM reflash, which I was told was to protect the new converter.
Since my Cherokee was (and still is) getting excellent gas mileage, I never had them put their paws on it.
 
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