Catalytic converter problems

[RAC02]

I have a 2001 wrangler and the check engine light came on. The code says the Catalyst converter is the cause. My question is would this cause intermeted sluggish acceleration? Could a head gasket cause the catalyst problems? Sometimes after the jeep warms up it has a sluggish acceleration. Could this be the catalyst converter or the engine? How would I know?

 

[Chris]

Absolutely. A clogged catalytic converter can indeed cause sluggishness, as could bad O2 sensors.

A bad catalytic converter will often glow red after driving around and sometimes there will be a sulfide smell, as well as decreased performance.

How many miles are on the cats? Mine went bad at 80k miles.

 

[RAC02]

I wish I knew. I just got this jeep and I'm having the cats looked at tomorrow. I have noticed a couple of times when the jeep has been running a while it does not have the same get up. But not all the time. Mainly when the jeep has been driving a while. My biggest concern is what caused the catalyst converter to go bad? What part of the compression system is letting the gas in there? What could cause the power concern the catalyst converter or whatever caused it to go bad in the first place.

 

[RAC02]

The check engine code lets me know the catalyst issue.

 

[RAC02]

Could the lack of acceleration being cause by catalyst converter be intermittent and more common under extended driving times or is that more common of a engine issue? Like head gaskets? I know head gasket issues can mess up catalyst converters. What the chances of this?

 

[11555h]

I have a 2001 4.0L and mine seemed to lose power for a short time one day last week. A couple of days later the check engine light came on and Coded PO420 & PO432. The garage cleared the codes and did a back pressure test which they said was ok. The light hasn't come back on yet. However I did discover that my Jeep should have 2 mini-cats just below the exhaust manifold which are not there and I'm wondering how that affects the O2 sensors and the computer. Afraid I can help you because I haven't figured mine out yet, but if yours is a 4.0L it should have 3 cats I believe. I planning on adding the 2 up by the exhaust manifold.

 

[RAC02]

Well took it to the cat guy and he said the cat was fine. Now I'm confused.

 

[RAC02]

And mine does have 3 cats

 

[mots]

Well took it to the cat guy and he said the cat was fine. Now I'm confused.

And mine does have 3 cats

What are the exact codes are you getting when the CEL comes on? Make sure you note exactly what they are before you clear them each time. I take a picture with my phone when I do this on any car.

You can read the codes on a TJ even without a scanner if you don't have one.


When my pre-cats were bad at 102k, I would periodically get the P0421 code by itself (Warm Up Catalyst Efficiency Below Threshold). While getting this code doesn't 100% mean bad cats, it is more than often the case. Getting this code solely by itself without other codes almost always means the cat isn't up to snuff. Mine would also pop O2 codes once in a while, but typically it was the sole P0421 code that convinced me to change the out the cats. You can buy a midpipe with all 3 cats for around $250, plug and play. This is what I did after getting tired of clearing the CEL and checking the codes all the time. I also replaced all 4 O2 sensors at the same time. I also found partial clogging due to physical degradation in the precats. After the repairs, no CEL for over a year now and the Jeep runs much better now, especially under heavy load.

 

[Quigley]

I’d start with new up stream o2 sensors NTK or NGK brand and see if that clears up your issues. If you still show the cat code it’s most likely the precats breaking down inside. I found my front pipe for $250 off eBay. I also ended up replacing the main cat and muffler back. I figured the exhaust was original an I had to drop it anyway to do the front pipe. Just start spraying for front pipe to manifold nuts and 02 sensors now with liquid wrench or kroil.

 

[skrelnik]

What are the exact codes are you getting when the CEL comes on? Make sure you note exactly what they are before you clear them each time. I take a picture with my phone when I do this on any car.

You can read the codes on a TJ even without a scanner if you don't have one.


When my pre-cats were bad at 102k, I would periodically get the P0421 code by itself (Warm Up Catalyst Efficiency Below Threshold). While getting this code doesn't 100% mean bad cats, it is more than often the case. Getting this code solely by itself without other codes almost always means the cat isn't up to snuff. Mine would also pop O2 codes once in a while, but typically it was the sole P0421 code that convinced me to change the out the cats. You can buy a midpipe with all 3 cats for around $250, plug and play. This is what I did after getting tired of clearing the CEL and checking the codes all the time. I also replaced all 4 O2 sensors at the same time. I also found partial clogging due to physical degradation in the precats. After the repairs, no CEL for over a year now and the Jeep runs much better now, especially under heavy load.

What brand of midpipe did you go with? How long was the install and was it painful to install, or relatively straight forward?

 

[mots]

What brand of midpipe did you go with? How long was the install and was it painful to install, or relatively straight forward?

We used the Flowmaster midpipe. We replaced the whole exhaust from manifold back at the same time. The catback used was the Banks Monster and it was also right around $250. So, about $500 for a plug and play manifold back system with 3 cats. Not bad in my book. It wasn’t super hard to install...removing the old 13 year old exhaust off was the biggest chore...getting off those old crusty fasteners. Doing just the midpipe alone could be a tad trickier I guess.

 

[RAC02]

What are the exact codes are you getting when the CEL comes on? Make sure you note exactly what they are before you clear them each time. I take a picture with my phone when I do this on any car.

You can read the codes on a TJ even without a scanner if you don't have one.


When my pre-cats were bad at 102k, I would periodically get the P0421 code by itself (Warm Up Catalyst Efficiency Below Threshold). While getting this code doesn't 100% mean bad cats, it is more than often the case. Getting this code solely by itself without other codes almost always means the cat isn't up to snuff. Mine would also pop O2 codes once in a while, but typically it was the sole P0421 code that convinced me to change the out the cats. You can buy a midpipe with all 3 cats for around $250, plug and play. This is what I did after getting tired of clearing the CEL and checking the codes all the time. I also replaced all 4 O2 sensors at the same time. I also found partial clogging due to physical degradation in the precats. After the repairs, no CEL for over a year now and the Jeep runs much better now, especially under heavy load.

That is the code I'm getting. I turn the key 3 times to retrieve the code. I'm shocked the cat guy said the cats are good... it makes me worried about what would trip the code. Do you have a link of the replacement for $250.00.

What are the exact codes are you getting when the CEL comes on? Make sure you note exactly what they are before you clear them each time. I take a picture with my phone when I do this on any car.

You can read the codes on a TJ even without a scanner if you don't have one.


When my pre-cats were bad at 102k, I would periodically get the P0421 code by itself (Warm Up Catalyst Efficiency Below Threshold). While getting this code doesn't 100% mean bad cats, it is more than often the case. Getting this code solely by itself without other codes almost always means the cat isn't up to snuff. Mine would also pop O2 codes once in a while, but typically it was the sole P0421 code that convinced me to change the out the cats. You can buy a midpipe with all 3 cats for around $250, plug and play. This is what I did after getting tired of clearing the CEL and checking the crodes all the time. I also replaced all 4 O2 sensors at the same time. I also found partial clogging due to physical degradation in the precats. After the repairs, no CEL for over a year now and the Jeep runs much better now, especially under heavy load.

P0421 is the code. Do you have a link for the $250 with 3 cats? Even though the cat guy said it was ok I believe they are still bad. It's the only thing that makes sense. I just hope it's not a engine issue that is making them heat up.

 

[RAC02]

I’d start with new up stream o2 sensors NTK or NGK brand and see if that clears up your issues. If you still show the cat code it’s most likely the precats breaking down inside. I found my front pipe for $250 off eBay. I also ended up replacing the main cat and muffler back. I figured the exhaust was original an I had to drop it anyway to do the front pipe. Just start spraying for front pipe to manifold nuts and 02 sensors now with liquid wrench or kroil.

The place I got it from said they changed one of the upstream o2 sensors probably not the NTK or NGK brand. So I could look at that to.

 

[astjp2]

The only real problem a can will typically get is clogged, if it is clogged, take a broom handle and knock a hole through the media. If it gets your acceleration back, you know that was the problem. If you dont like that option, get the O2 sensors and swap them. Not having upstream cats should not affect the upstream o2 sensors.

 

[mots]

That is the code I'm getting. I turn the key 3 times to retrieve the code. I'm shocked the cat guy said the cats are good... it makes me worried about what would trip the code. Do you have a link of the replacement for $250.00.

P0421 is the code. Do you have a link for the $250 with 3 cats? Even though the cat guy said it was ok I believe they are still bad. It's the only thing that makes sense. I just hope it's not a engine issue that is making them heat up.

I used Flowmaster part # 2049170, but this model is only for 04-06. You should be able to find a similar direct fit replacement for your 2001, just not sure Flowmaster makes anything.

 

[RAC02]

Well I just noticed the lack of power and the jeep started to shake. When I did pull over I noticed right above the cats a red glow. It was right above the mini cats. The funny thing is I only had the jeep cracked up for about 10 mins. Yes I was going around 55 but no faster as the shaking was to bad. I stopped for about 30 min and took it back out now everything is ok. I guess that would mean it's the mini cats?

 

[RAC02]

Ok so I need some help finding a 3 cat direct fit for 2001. I see the flowmast for 2004 but no 3 peice direct fit got 2001

 

[RAC02]

Would onw of these be a good choice?

 

[11555h]

Someone suggested to me to look at Rock Auto. I found a Walker front pipe with 2 mini cats for $328. They also have the rear cat as well but I think I'll just go with the front and see what the rear cat looks like when I get the front pipe off