1997 lean condition

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crowncrazy87

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Yea I've sprayed carb cleaner all around the thing already. A couple of times lol. Didn't do anything that I noticed. Checked fuel trims today. Bank 1 trims never went over 10 either way but the long term on bank 2 stayed between 18 and 26! Truck isn't really drivable so this was done at idle.
 

Killer Ride

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Another way to check for clogged cats is with a digital thermal temperature sensor. Point it at the headers on both sides. The hotter side will be the clog

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TobyU

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Sounds like a massive vacuum leak to me. I had one that i did the plugs on a 6.8 in a van and knocked the big hose that goes to air bypass valve off. It wouldn't run for crap of stay running...Massive leak. I thought I was screwed until I saw the hose off.
 

1955moose

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Actually when using a heat gun, you want to aim it at the front and rear of cat. A good cat will be hotter on the exit side, by at least 100 degrees. When clogged the exit is same or colder.

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Killer Ride

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Actually when using a heat gun, you want to aim it at the front and rear of cat. A good cat will be hotter on the exit side, by at least 100 degrees. When clogged the exit is same or colder.

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Actually the opposite is true, and the cats are directly bolted to the headers hence the reason to point the thermal sensor there nif there is a clog believe me it will be hotter above the cat

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1955moose

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Well killer your the first in almost 5 years that made a statement like that. Think about it, exaust flows off each manifold, runs through header, then through each cat. If theirs a blockage in one or more cat, heat is going to get trapped within the honeycombs, or whatever material. If you've ever seen a really stuffed up one, they glow red. Go online, and you'll see that a proper functional catalytic system will be about 275 front, and 350-375 rear. Anybody else want to jump in here? When using a 02 gauge to read back pressure, you want a low #, closer to 0 the better. Usually a plugged one reads 10 or higher.

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Killer Ride

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Yea thought about It,first off the heat stays trapped above the cat and usually it's the first one that gets clogged. I can put my hand on anything after that and it is only warm. Agree with you on the back pressure readings just did mine it reads 9

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1955moose

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Was their a loss of power? Did you replace cat's? Common sense would dictate that temp should reduce down the exaust trail, not go up. Engine headers can get close to 1200 degrees Fahrenheit, as the spent exaust makes it's way to the tailpipe it's dropped way down, put your hand there at tailpipe gases, feels no more than 150 degrees. I think the reason the cat temp goes up instead of down, is the conversion process of breaking all the bad stuff down, like nitric oxide, carbon monoxide, and other nasty things, and make them breathable. Anybody here old enough to remember the 70's remember that bad smog in Los Angeles, and other metro areas. In theory it sounds backwards like you said. I did read an answer from advanced Auto parts that confirmed your theory. But all the rest said higher not lower exiting towards rear. This weekend I'm going to check my Eddie Bauer, and see what temps I get. My Suv runs fine, with no misfires or fuel dumping, so I'm assuming mine are ok. As long as we don't get too much rain this weekend, I'll post my findings.

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Killer Ride

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Yes definitely lack of power can't wait to get them replaced it will be like brand new. Trust if your cats are plugged you will see high heat at it and above it downstream will be cool. I put my hand at end of tailpipe 5 min after start and it was cold and hardly anything was coming out

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1955moose

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See then the theory makes sense. All the heat is being trapped in the honeycombs of cat. When unburned gasses from say a bad exaust valve or misfiring coil or plug, gets stuck in the cat, and fuses in there. It's like soldering your passages in there. As expensive as catalytic converters are, it's amazing how many individuals don't fix a simple misfire, and then cry when they've got to plunk down a grand or more for exaust work!

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