Pre-cats and y-exhaust pipe repair (solved)

KCsTJ

KCsTJ

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Farmersville, TX, United States
I am troubleshooting a p0431 code on my 05 Sport, "warm-up catalyst efficiency below threshold, bank 2".

I have ordered both NTK o2 upstream sensors which may correct the problem.

However I plan to also replace the Pre cats as PM cuz it has 101k.

I plan to unbolt the 2 pipes connected to the exhaust manifolds, then cut the straight pipe before the cat convertor and attach or weld a pipe connector at that point.
Anyone done this or have any suggestions?
 
I have had bad luck with slip on connectors. Alwas seem to leak. I much prefer to have it welded. Down side to that it makes installation a little harder but not impossible.
 
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When I replaced the pre-cats on mine, I used the Walker replacement.

There are however a wide variety of replacements for your 2005, such as all of these below:

https://www.amazon.com/dp/B001AGP864/?tag=wranglerorg-20
https://www.amazon.com/dp/B06XMXC6YK/?tag=wranglerorg-20
https://www.amazon.com/dp/B0031G6YT6/?tag=wranglerorg-20

I removed my third cat entirely. If you live in a town that doesn't have inspections, you won't have to worry about removing the third cat. It also won't cause any check engine lights either, nor does it affect your emissions system. All it does is free up some room and make the exhaust a little throatier (in a good way).

I had a shop do this for me since it really needed to be on a lift to make it easier, but I used those Walker pre-cats linked to above on my 05.
 
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KCsTJ said:
Thanks @Chris ! Thats exactly what i needed!
I think I'll go with Eastern. Looks like it would bolt right up .
I think I'll remove the 3rd cat also, I like a throaty exhaust :)
Click to expand...

That's the way to do it! Mine sounds great with the third cat removed, and it clears up space as well, for whatever that's worth!
 
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My initial hunch paid off!
The initial code p0431 = catalyst efficiency below threshold, bank 2.
Replacing the pre cats would have cost around $300.

With some knowledge gained from this forum, I ordered both bank 2 oxygen sensors and installed them. Unhooked the negative battery cable for a few minutes.

Next day no cell codes! Beats $300 for a.pre cat exhaust!
 
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I'm getting an intermittent P0431 also. Jeep runs great with 57k on it. Anyone else remove third cat? Never heard of that before. I have access to a lift but without looking up there right now I'm not sure what it would take to remove it. I'm guessing I need a section of pipe at least.
 
Mike the Silver TJ said:
I'm getting an intermittent P0431 also. Jeep runs great with 57k on it. Anyone else remove third cat? Never heard of that before. I have access to a lift but without looking up there right now I'm not sure what it would take to remove it. I'm guessing I need a section of pipe at least.
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Intermittent P0431 suggests to me that your precat on bank 2 may be going out. That usually happens around 100k .... Maybe a new 02 sensor for bank 2 would resolve it, not certain but may work.
Intermittent makes it hard to diagnose.
 
I was having the P0431 as well. Replaced all four O2 sensors and great for a while. Now the check engine light came on with P0431 again. I checked again and found the rear pre-cat was loose. I tightened up the bolts and it cleared on its own. Jump ahead one month and the light comes back on with P0431 again when the fuel tank reached 3/4 full. I read another thread where someone else ran into the same problem when the tank got down to 3/4. I ran up to the gas station, filled the tank, started it and the check engine light cleared itself. Strange.

Has anyone else seen this before I pull the cats and check them?
 
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MikeM1554 said:
I was having the P0431 as well. Replaced all four O2 sensors and great for a while. Now the check engine light came on with P0431 again. I checked again and found the rear pre-cat was loose. I tightened up the bolts and it cleared on its own. Jump ahead one month and the light comes back on with P0431 again when the fuel tank reached 3/4 full. I read another thread where someone else ran into the same problem when the tank got down to 3/4. I ran up to the gas station, filled the tank, started it and the check engine light cleared itself. Strange.

Has anyone else seen this before I pull the cats and check them?
Click to expand...
Ever figure out if it was the pre-cat or not?
 
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A few days ago I replaced my precats with a Magnaflow precat. I cut the existing pipe and have had no problem with an exhaust leak. The Magnaflow is mandrel bent and right now it's pricey. Amazon had it for almost $200 less than anyone else.
 
Charlie L said:
A few days ago I replaced my precats with a Magnaflow precat. I cut the existing pipe and have had no problem with an exhaust leak. The Magnaflow is mandrel bent and right now it's pricey. Amazon had it for almost $200 less than anyone else.
Click to expand...

Did the Magnaflow come with the 4 O2 sensor ports? Have link to the one that you purchased?

I am looking to replace my cats on my 06 LJ Rubi and can't find one with 4 ports and long wheel base.

Replaced all 4 sensors and the PO431 code came back.
 
After posting above, I went out and looked at my Jeep. I see the 2 precat O2 sensors are on the manifold, so that is why the cat converters only come with 2 ports….
 
Fire814 said:
After posting above, I went out and looked at my Jeep. I see the 2 precat O2 sensors are on the manifold, so that is why the cat converters only come
Click to expand...
Fire814 said:
After posting above, I went out and looked at my Jeep. I see the 2 precat O2 sensors are on the manifold, so that is why the cat converters only come with 2 ports….
Click to expand...


It has two sensor ports, the only thing you may need are longer mounting bolts. I fought trying to mount it withe existing bolts and finally gave up and bought some that were 1/2" longer. Amazon Magnaflow 50899 $753.18.
 
Did you add the 3 cat?
What does the Magnaflow sound like compared to before you replaced it?
 
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