zippy Posted January 8, 2008 Report Share Posted January 8, 2008 Why do you need to gut them? The aftermarket high flow cats often will set codes and rarely plug up. They tend to just not be as efficient at lowering the amount of unburnt gasses getting past them to the rear sensors. Pretty much everyone that has long tubes with aftermarket high flow cats will get codes if they don't turn off the rear O2's. Quote Link to comment Share on other sites More sharing options...
Black2003SS Posted January 8, 2008 Report Share Posted January 8, 2008 I get codes on long trips on my rear O2's...I want to just put in a set of straight pipes. Quote Link to comment Share on other sites More sharing options...
dcairns Posted January 10, 2008 Report Share Posted January 10, 2008 I was getting an: P0430 Engine controller ($10) - - - - - - C - Catalyst System Efficiency Below Threshold (Bank 2) GM said it was the cats, and wanted $1200 to replace them (they blamed the supercharger and would not warranty them). So I bought some slightly used cats from foxySS (thanks ), who was going with some high flow cats, and had the stockers laying around. That solved my problem. The old cats looked fine visually. Probably just cooked off the platinum enough to reduce their efficiency. Quote Link to comment Share on other sites More sharing options...
SSThunder Posted January 11, 2008 Author Report Share Posted January 11, 2008 Why do you need to gut them? The aftermarket high flow cats often will set codes and rarely plug up. They tend to just not be as efficient at lowering the amount of unburnt gasses getting past them to the rear sensors. Pretty much everyone that has long tubes with aftermarket high flow cats will get codes if they don't turn off the rear O2's. Hi Zippy, I'm worried that code means my cat is clogging up. I've had the headers and high flow cats on for awhile and never got the code till after I added the radix and put on the 3.0 pulley. I'm afraid if I turn the code off and they clog, i'll be saying bye-bye to my engine. Does naybody know the signs of a clogged cat? Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted January 12, 2008 Report Share Posted January 12, 2008 (edited) Does naybody know the signs of a clogged cat? Jeremy there are a few signs........ A rancid rotten egg smell Extremely poor gas mileage A loud rattle at certain RPMs Do you have true duals? If so place your hand by the tailpipe with the engine running, you should feel the exhaust pressure blowing against your hand.........if not, the cat is most likely clogged. Edited January 12, 2008 by Fireman31 (see edit history) Quote Link to comment Share on other sites More sharing options...
SSThunder Posted January 12, 2008 Author Report Share Posted January 12, 2008 Jeremy there are a few signs........A rancid rotten egg smell Extremely poor gas mileage A loud rattle at certain RPMs Do you have true duals? If so place your hand by the tailpipe with the engine running, you should feel the exhaust pressure blowing against your hand.........if not, the cat is most likely clogged. Dan, I don't have any of those so I might just turn the code off and monitor the engine and see how she does. I don't have true duals. Quote Link to comment Share on other sites More sharing options...
YenkoChevelle69 Posted January 23, 2008 Report Share Posted January 23, 2008 My truck threw that code, then a misfire code. It was plugged up solid! I cut the pipe directly behind the cat and then ran the truck. I glowed orange so I busted out the guts of the cat and it ran like a scalded cat! Quote Link to comment Share on other sites More sharing options...
zippy Posted January 25, 2008 Report Share Posted January 25, 2008 Dan, I don't have any of those so I might just turn the code off and monitor the engine and see how she does. I don't have true duals. Check around to the guys that are running long tubes and aftermarket cats. You'll find that most of them have the exact same issue. The cats aren't plugged, but they simply aren't reducing the emissions enough to keep the light off. Quote Link to comment Share on other sites More sharing options...
SSThunder Posted January 26, 2008 Author Report Share Posted January 26, 2008 Check around to the guys that are running long tubes and aftermarket cats. You'll find that most of them have the exact same issue. The cats aren't plugged, but they simply aren't reducing the emissions enough to keep the light off. I don't have any signs of a bad cat so I loaded your new tune that turns the code off and it's running fine. Quote Link to comment Share on other sites More sharing options...
Turbocoop Posted January 29, 2008 Report Share Posted January 29, 2008 I took out my cats today and put in flex pipe sections and its waaaaay too loud. I knew it would be louder but it sounds like it did when I had no muffler, its sick. I guess I gotta get used to it though cause my new pcm is tuned for no cats Quote Link to comment Share on other sites More sharing options...
slammedbowtie Posted February 14, 2008 Report Share Posted February 14, 2008 i had a plugged up solid cat last week. truck would barley run. i had codes, P-0101, P-0300, and 2 codes for P-0430. put hi flows on and damn the truck came alive. might have been semi clogged for a while. and its way! louder now also. i love it, and its tech legal! Quote Link to comment Share on other sites More sharing options...
chevydeth Posted February 20, 2008 Report Share Posted February 20, 2008 I had the 420 code, it was clogged cats. however it was still covered up GM's warranty. I didn't pay a dime. This happened about 2 years ago and its a 99 so your probably still covered. Quote Link to comment Share on other sites More sharing options...
Black Beast Posted February 20, 2008 Report Share Posted February 20, 2008 if you bust out the cats do you still get the rancid rotten egg smell? Also, In N.C. the plug up a computer to your OBD and run test. Will they be able to "see" that the cats are gone? Quote Link to comment Share on other sites More sharing options...
chevydeth Posted February 21, 2008 Report Share Posted February 21, 2008 Mine never even smelled, just when i accelerated it seems like it hesitated and made a breaking up sound. Then the code.. Quote Link to comment Share on other sites More sharing options...
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