Is my catalytic converter about to shit itself?

DropTopDon

TJ Enthusiast
Joined
Nov 7, 2019
Messages
642
Location
VA


In a new to me LJ I have been hearing this rattling noise at start up. It gets drowned by engine noise and music when driving but it is still slightly there when driving too. Some times it will go away though. The PO told me it was because "the cat is rattling against the transmission". Upon initial inspection it did look this way because the cat was resting on the corner of the transmission. Since my ownership I have installed a suspension and body lift so there is no longer contact with the cat and the transmission so obviously that isn't why it is rattling. I also just got a P0432 code "catalytic converter operating below minimum efficiency". I got out and put my ear to the third cat and it sounds like a coin is bouncing around in there. Where should I go from here?
 


In a new to me LJ I have been hearing this rattling noise at start up. It gets drowned by engine noise and music when driving but it is still slightly there when driving too. Some times it will go away though. The PO told me it was because "the cat is rattling against the transmission". Upon initial inspection it did look this way because the cat was resting on the corner of the transmission. Since my ownership I have installed a suspension and body lift so there is no longer contact with the cat and the transmission so obviously that isn't why it is rattling. I also just got a P0432 code "catalytic converter operating below minimum efficiency". I got out and put my ear to the third cat and it sounds like a coin is bouncing around in there. Where should I go from here?

The third cat won't trip that code, only the precats. You can test them a few ways, one easy one is to get an IR thermometer and check the input temp and output temp. The rear on a good cat is typically higher than the front.
 
If you’ve got any mileage at all it’s ready for cats- i’ve ran into it twice at 70,000 and over on later model ones- Rumor has it that the earlier catalytic converter’s are tougher on all vehicles

Sort of sounds like planned obsolescence

You can also remove one of your 02 sensors and easily run the scope into the hole and see the media in the swell , and if the media is dropping you’ll see it right there at the sensor



This is not a qualified statement but it seems to me the rear bank fails first
 
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When my cat was about to shit itself, it looked more like this. :unsure:
p.s. My main cat rattled like Hell when it went bad. Sounded like it was coming from the trans at idle.
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Bang on the cat with a rubber mallet (engine off). If it's breaking up inside you should hear it rattle.

When my '97 Dodge pickup did that, the broken pieces in the cat plugged up the outlet hole, which made the truck run absolutely terrible. I drove it to a shop to get it fixed, which was a big mistake. The plugged exhaust heated the whole system so bad it warped the exhaust manifold, which popped a couple of bolt heads. If it plugs, don't drive it.
 
Confirmed it is the rear wards pre-cat. Put my ear next to it and it is banging like crazy. A friend told me I can save money by just gutting all three cats and putting it back in. Can I do that or is there something wrong with that?
 
Confirmed it is the rear wards pre-cat. Put my ear next to it and it is banging like crazy. A friend told me I can save money by just gutting all three cats and putting it back in. Can I do that or is there something wrong with that?

If you gut all three cats, you'll definitely set a check engine light. Assuming it isn't perma-lit already.
 
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If you gut all three cats, you'll definitely set a check engine light. Assuming it isn't perma-lit already.

What you’re getting into is really doing something that the computer doesn’t know how to deal with- I’m all for airflow at the same time those sensors tell the computer to make adjustments that it can’t do if there’s nothing to read correctly- In addition to a check engine light you may get into some performance issues that negate losing the restrictions-

I’ve never seen these jeeps run any better than when you freshen them up to stock parameters- At the same time if you’re going to delete a cat the one down stream would be the one to do and you can get a really good exhaust tone.
 
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Few different choices I have right now.

https://www.amazon.com/Evan-Fischer-REPJ960313-Catalytic-Converter/dp/B06XMXC6YK

Has anyone had good/bad experience with evan fischer? Has all 3 cats for $428.

Or I could go with https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20

I’ve heard good things about Walker. It doesn’t have the third cat though so what substitutes in in the area that the third cat should be If it is deleted?

I found this one too for only $274 but I’ve never heard of them
 
Mine 2004 cats went out at about 70,001 miles, pretty much the day after the warranty expired. The replacements are still working but I have a feeling they are on borrowed time. You only need the two front little guys to keep the computer happy.

This seems like a really good deal.
Wonder why it says; doesn't fit LJ?

Funny they specifically exclude the Unlimited, nothing different up front really except the hood insulation and some little patch on the frame rail from what I remember. It's possible they just didn't pay to get the Federal certification for the Unlimited models.
 
Man I’ll tell you how it goes with catalytic converter’s and oxygen sensors-

It’s one of those things you really don’t want to think there’s anything wrong and you’re a little hesitant to spend the money and it won’t fix the problem-It’s a lot easier to spend that kind of money on a set of wheels or something to look at

And at the same time I’m all for not just throwing money at the problem

But I believe on any 04-06 TJ or LJ with over 70,000 miles it’s a pretty safe gamble that you need them and that you’re going to enjoy the improvement.

I have found myself clearing a code multiple times thinking that I’m going to make it go away and buying better gasoline and additives and all kind of stupid stuff but eventually bite the bullet and it’s worth the money every time.

I have a 2006 and it developed a knock and rattle like it had valve train noise and a piston slapping- It really would have been hard to convince someone buying it that it didn’t have a real problem- I had a really really accomplished and successful mechanic look at it and he was confident that it didn’t have engine trouble but we just couldn’t pinpoint the problem- And this is the guy that fixes things that the dealers can’t fix which isn’t always saying a lot these days...

New cats, spark plugs and oxygen sensors fixed it and basically it was running with one cylinder that just wasn’t firing at the right time, fully or whatever- It literally runs like a sewing machine now