buyer beware
#15
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If your cats(or muffler) are clogged that pressure has to escape somewhere. The same amount of air that came into the engine must find its way out. If it can't get out the exhaust where can it escape? That only leaves valve overlap. The exhaust that can't escape out the tail pipe looks for the next easiest route which just happens to be a different exhaust valve which just happens to have its associated intake valve open at that time(overlap). This kills power and performance and gas mileage BIG TIME. You should have noticed this while driving. This isn't the kind of thing that happens all of a sudden. It occurs slowly over time as the cat breaks up into small pieces which takes a while. Did you notice it was down on power?
Last edited by eallanboggs; 10-26-2008 at 01:03 AM.
#16
Yeah, I did notice but my commute to work every day is only 10 minutes so It is hard to notice a lot of a difference in a 10 minute drive. If I got on it it would still blow ths tires off so I just figured the tune was off or I lost some low end. The mufler was not completely clogged up but I couldn't see what was in there so I just got rid of it but on my drivers side stuck on the rear O2 sens or was a huge mound of metal. There was a lot of **** in there and my truck was running bad the day after install so I think the cat's did not last too long.
#18
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Sometimes a clogged cat is hard to diagnose. Yours is even harder because you don't expect the cat to break up into small pieces by itself. That's unheard of. So what you ended up with is a hollowed out cat and a clogged muffler as a result of the cat coming apart. That's a new one. Usually the cat will clog up. That's not to say the muffler can't get clogged, but more often than not it's the cat that goes south. You have to use and Exhaust Gas Backpressure Tester to pinpoint the problem area. You take pressure measurement at the 02 bungs. You should see low pressure at the pre cat bung and a slight increase at the post cat bung. I your case there would have been no difference since the cats had gutted themselves. Both reading would have been too high since the muffler was clogged which would have caused both pre and post cat reading to be over the limit. This would have pointed to the muffler as the problem, but I doubt you would have concluded that the cat had gutted itself from the pressure readings. The only time I've see a gutted cat is when I took a plumbers snake I had chucked up in my electric drill and roto rooted the cat. Funny how that seems to unclog those cats real quick.
#19
actually, the isides of the drivers side cat stayed intact in a huge clump and got stopped by the O2 sensor behind the cat. This is how we initially knew we had some sort of blockage. When I checked the passenger side and found nothing I was pretty sure it would be in the muffler.
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