Had to get new Catalytic Convert to pass emissions today... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-03-2003, 12:40 AM   #1
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Default Had to get new Catalytic Convert to pass emissions today...

My cat was split open on the edge and leaking fumes. Thus makin my car a lil noisier which I thought the xtra noise was from the 4" duct CAI i made. Car is quieter now. My question is how to these things go bad and does the fact that I need a new PCM (powertrain control module) put an xtra strain on the cat?
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Old 01-03-2003, 12:47 AM   #2
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The PCM doesn't really know the Cat is there. Doesn't really care unless you're running dual O2'* in the newer models.

These things can go bad in several ways. Lots of short trips cause moisture to build up and sit, running rich for extended periods of time, storing your car for extended periods (that caused the demise of my Cat), or just poor craftmanship. You might have had a manufacturing flaw....bad weld, poor sheet metal, etc.

I'm not really sure how long these usually last. Jrs3800 can give us a much better breakdown on Cats.
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Old 01-03-2003, 02:10 AM   #3
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Autosound Hi flow. Made a noticeable difference. I oversized it too. It'* the model usually used on a full size chevy pickup......with the 350. I should be pretty 'invisible' to my exhaust system. Methinks it was about 125. Talk to Ty, though. I remember him saying he had a line on Cats.
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Old 01-03-2003, 01:38 PM   #4
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I just changed my CAT about a month ago or so, the factory unit lasted me 172 000 kms or ah...lemme convert OK..106K miles....it rusted out at the connection between the manifold and the converter. It was really really loud..didn't like it

I got the muffler shop to weld and bolt together the new cat to the manifold. I suggest stainless steel. It won't rust. After all the ,undercarriage of our poor cars takes a beating...esp in winter..god I hate winter....

Good luck
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Old 01-03-2003, 02:22 PM   #5
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I know my cat is going...my car gets louder and louder every day.
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Old 01-03-2003, 03:11 PM   #6
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Unless ist'* rusting through, the typical failure in a cat is the grids inside rusting and falling apart. I had a horrible rattle at idle and as I accellerated. Everyone thought my tranny was falling apart!
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Old 01-04-2003, 09:09 PM   #7
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if you ever had the inside of a cat apart, its a very simple thing. it is a grid of tiny squares the length of the cat. making the exhaust flow through it. this grid is a ceramic material. when you run rich, it puts unburnt fuel in to the cat. when this happens, it burns in the cat. casuing it the melt down and plugging it. also repeated heat cycles can make it brittle and falling apart inside. this will cause a rattle and can restrick the exhaust causing lose of power. if you run with a restricted cat for too long, you can burn valves, or even catch the car on fire due to the excess heat in the cat. a cat has one purpose, with the heat in the cat, the material that the cat is made of, it creats a chemical reaction iside of it. this is why you see water coming out of your tail pipe.
exhaust starts out as carbon monoxide(CO )and hydrocarbons (unburnt fuel) after going through the cat. it converts it to carbon dioxide (CO2) and H2O(water) both of which are nontoxic.
fuel managment is very important when it comes to making you cat survive. anytime the SES light comes on, you need to have it fixed ASAP . the pcm tries to keep your air/fuel ratio at 14.7:1 this isnt for performance bu for the EPA to be happy.
hope this helped understand how a cat works and how to make one live
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