4.0L catless?

99ncxj

99ncxj

Well-Known Member
Joined
Sep 23, 2006
Location
Aliso Viejo, CA
Anyone know what is needed (if anything) to run an HO 4.0L without a cat? Its got an O2 sensor in it so if i need to weld in a bung somewhere in the exhaust to make the computer run right I can. Any performance losses when doing this?

The only reason i'm considering it is with my pass side drop front axle, i'm going to have to re route the exhaust down the drivers side and if i don't have to deal with installing the cat back in there it would make it easier.
 
I removed mine..seems to still run fine..maybe a little bit better...maybe.

My check engine light stays on though.
 
Dylan W. said:
I removed mine..seems to still run fine..maybe a little bit better...maybe.
My check engine light stays on though.
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did you move the cat O2 sensor back into the exhaust somewhere or just leave it unhooked?
 
Mines off. My o2 was knocked off long ago too. Still runs as "fine" as it did before. Actually better since the cat was clogged.
 
I'm not really concerned with the sound. Actually, I'd like to make it a little quieter than it was with the cat/cherrybomb.

I've got a flowmaster muffler to put on it and will have a short down turn right out of the muffler so hopefully it won't sound like crap.
 
99ncxj said:
I'm not really concerned with the sound. Actually, I'd like to make it a little quieter than it was with the cat/cherrybomb.
I've got a flowmaster muffler to put on it and will have a short down turn right out of the muffler so hopefully it won't sound like crap.
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It won't sound like crap, it will actually sound really good. I had the same setup on my old 91 XJ. It won't be quiet though. It is louder than a cherry bomb.
 
Yeah, and watch out how you make that ''turn'' underneith...just make sure the fumes dont get ya sick or dead.

I have a 40 series Flowmaster on mine...sounds ok to me.
 
yodaman88 said:
what would be needed to remove the cat without the check engine code?
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cannot be done. the whole purpose of that o2 sensor behind the cat is to monitor the cat's efficiency and let the computer know if it has a problem. maybe a custom chip or something.
 
jeepman13 said:
cannot be done. the whole purpose of that o2 sensor behind the cat is to monitor the cat's efficiency and let the computer know if it has a problem. maybe a custom chip or something.
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A simple resistor works. But it's not worth the effort in an offroad only vehicle...

Can also be done by screwing a sparkplug non-fouler in front of the sensor. Or at least I've been told.
 
braxton357 said:
A simple resistor works. But it's not worth the effort in an offroad only vehicle...

Can also be done by screwing a sparkplug non-fouler in front of the sensor. Or at least I've been told.
Click to expand...


sounds like good ideas to bypass. totally agree it's not worth it in an offroad only vehicle.
 
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