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Catalytic converter questions

3K views 11 replies 9 participants last post by  Astro Pop 
#1 ·
So my CAT is fried. She rattles like hell. Ever since i changed my sparks, she's run better but rattles more. MPG went up, the sparks looked original ( have 121k) and since i bought it at 118k, its had a p0420.

montana laws dont have emissions, so is it legal to run without a cat? I want a cheap fix. Can i cut the cat out, and replace with a small section of exhaust pipe, fitted with hose clamps? Or does it have to be welded?

or should i just buy a new cat, will it help/hurt my MPG?

I'm looking for good MPG, cheap fix. I have a friend who can weld, but it may take weeks to get him in gear.

Thanks!
 
#2 ·
Hose clamps, absolutely not. They'll never seal exhaust gas.

I'll say replace the cat. You'll have less emissions getting into that beautiful Montana air when you drive to Saint Alphonsos Pancake Breakfast.

Others will say weld in a straight pipe and your performance and MPGs will improve by 136% at least.

Lump
 
#4 ·
I'd recommend getting a new cat. It just doesn't make any sense to me to cut and weld on a straight pipe instead of a cat.. it's the same amount of work. You can get a cat for less than 100 bucks shipped.. and do it the right way. The performance gains of a straight pipe is very negligible.. especially since our vans aren't high performance to begin with. Heck, if you know some recyclers you may even get some money back for your old one.
 
#6 ·
The cat is part of the emission control system. Montana might not have laws against it, but it is against federal law to do it. That said, I have read of instances where the converter was hollowed out and reinstalled. Again, against federal law to tamper with emissions equipment.
 
#7 ·
Big_kid said:
The cat is part of the emission control system. Montana might not have laws against it, but it is against federal law to do it. That said, I have read of instances where the converter was hollowed out and reinstalled. Again, against federal law to tamper with emissions equipment.
And if you read the fine print of the law. That applies to professional shops installing non cat exhaust. Just sayin.
 
#12 ·
These vans are computer controlled. If you take the cat out then the O2 sensors will give you fits, so then you have to buy more parts to by pass the sensors to avoid codes popping up..... Best bet, buy a new cat and be done with it. The mileage gained is so minimal it just isn't worth it.
 
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