Cat Removal Question
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Junior User
Joined: Nov 2004
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Cat Removal Question
I have a bad catalytic converter on my work truck (98 f-150 4.6L). is there a way to just remove it and trick the computer into thinking it is still there and working properly? also, it is in Illinois and we have to get emissions tested every two years - will this throw up a red flag? they just plug into the computer and check for codes, no visual inspection.
Super Moderator
Joined: Apr 2004
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Does your system have a sensor after the cat? Do they put a sniffer in the tail pipe? If so, you won't pass w/o the cat.
How do you know it's bad? My smog man was telling be replacement cats is a real problem business. He's had cars come in with a "new" cat that were worse than with the old one. If you replace it, go with an OEM part and resist the cheapo items that may or may not do the job. But make sure it's the cat and not something else.
How do you know it's bad? My smog man was telling be replacement cats is a real problem business. He's had cars come in with a "new" cat that were worse than with the old one. If you replace it, go with an OEM part and resist the cheapo items that may or may not do the job. But make sure it's the cat and not something else.
Tuned
Joined: Dec 1999
Posts: 464
Likes: 1
From: Bismarck USA
Well, first off, I'd be curious how you know your cat is bad. Some codes will state that, but the real culprit is the EGR system or some other point. Not the cat itself.
Assuming the cat is bad, that would mean it's clogged. If that's the case, it's gotta go. I suppose you "could" take it off and gut it and put it back on. Then there's no back pressure from the cat. So you'd need a good muffler. Otherwise you're basically running straight pipes.
Then you probably have two "downstream" O2 sensors after the cat. If you do, you'd have to feed a false signal to the computer. I think O2 sensors work on a specific voltage range. Something like 1.5 -2 volts, or something like that. So you'd have to feed a false voltage to those wires once you know the correct running voltage.
All of that is assuming you know you're breaking federal emissions laws by bypassing the cat. :-)
Assuming the cat is bad, that would mean it's clogged. If that's the case, it's gotta go. I suppose you "could" take it off and gut it and put it back on. Then there's no back pressure from the cat. So you'd need a good muffler. Otherwise you're basically running straight pipes.
Then you probably have two "downstream" O2 sensors after the cat. If you do, you'd have to feed a false signal to the computer. I think O2 sensors work on a specific voltage range. Something like 1.5 -2 volts, or something like that. So you'd have to feed a false voltage to those wires once you know the correct running voltage.
All of that is assuming you know you're breaking federal emissions laws by bypassing the cat. :-)
Hotshot
Joined: Jun 2003
Posts: 12,334
Likes: 4,345
From: SW VA
If it is clogged, take it off, gut it and put it back on. Get O2 simulators so the computer will think the cats are still there and doing their job. Also, your CEL wont come on and the emissions testing computer thing will still think the cat is working properly and wont throw any red flags.
http://www.o2sensorsimulator.com/
http://www.o2sensorsimulator.com/
