1987 TBI 454 Suburban... It Runs! Kinda.

Northernregal

Northernregal

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Oct 24, 2017
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I need to see the end of this movie. It's just getting good.
 
MrSony

MrSony

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TURNA

TURNA

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pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
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Kitchener, Ontario
Well...
i did the cheap code thing with the paper clip.
Just 12. Stared at it for 5 minutes.
12.

I think, however, the exhaust is plugged up. Nadda comes out of the pipes, and it has that shitty old pellet type converter, there was evidence of mice under the hood so they could very well have built a nest in the exhaust while it was sitting. I'm gonna cut the cat off this weekend and see how it runs, if at all, unrestricted.
You don't need to guess, use a laser temp gun and check the temperature before and after the cat. It should be cooler in front of the cat. If it's the same temp or higher in the front the cat is defective.
 
69hurstolds

69hurstolds

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Jan 2, 2006
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You don't need to guess, use a laser temp gun and check the temperature before and after the cat. It should be cooler in front of the cat. If it's the same temp or higher in the front the cat is defective.
Without a code reader for those with dual O2 sensors, it's a bit more difficult to tell if a cat has failed. You certainly don't want extra rich fuel running through which will burn up your catalyst material prematurely. Very slightly lean then rich cycling is the sweetspot for most modern day cats due to the dual nature of the NON-A.I.R. style cats with sustaining O2 levels and still have NOx reduction.

But as far as inlet and outlet temps, I thought it was the other way around. Slightly cooler in back is fine, but if it's significant difference in temps, there's likely issues. Cats shouldn't generate more heat than what's coming in or something is wrong, like raw fuel getting to the cat. Vacuum gage can also tell you if there's blockage. At mid-range rpm if vacuum starts to drop off, something might be wrong with the cat flow.

Of course, cutting off the cats will definitely eliminate them from the troubleshooting equation.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
24,750
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Kitchener, Ontario
Without a code reader for those with dual O2 sensors, it's a bit more difficult to tell if a cat has failed. You certainly don't want extra rich fuel running through which will burn up your catalyst material prematurely. Very slightly lean then rich cycling is the sweetspot for most modern day cats due to the dual nature of the NON-A.I.R. style cats with sustaining O2 levels and still have NOx reduction.

But as far as inlet and outlet temps, I thought it was the other way around. Slightly cooler in back is fine, but if it's significant difference in temps, there's likely issues. Cats shouldn't generate more heat than what's coming in or something is wrong, like raw fuel getting to the cat. Vacuum gage can also tell you if there's blockage. At mid-range rpm if vacuum starts to drop off, something might be wrong with the cat flow.

Of course, cutting off the cats will definitely eliminate them from the troubleshooting equation.
the exhaust temp is increased in the cat due to some restriction but if the cat is partially plugged the heated exhaust will cause the exhaust in front of the cat to heat up
 
69hurstolds

69hurstolds

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Jan 2, 2006
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the exhaust temp is increased in the cat due to some restriction but if the cat is partially plugged the heated exhaust will cause the exhaust in front of the cat to heat up
??? Umm. Ok. Now you're saying the outlet temp would be higher on a normal flowing cat, but significantly less than inlet temp for the cat if it's plugging? I agree with the 2nd part. I'm no expert, but we'll just have to disagree about the heat transfer aspect of a normal cat converter. I still maintain if the outlet temp is higher than inlet, there is something going wrong (usually over-rich) and your cat(s) eventually will die.

Doesn't matter anyway if cutting off the cats. Back to the saga....waiting to see if exhaust flow restoration is the ticket.
 
TURNA

TURNA

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Jul 24, 2009
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You don't need to guess, use a laser temp gun and check the temperature before and after the cat. It should be cooler in front of the cat. If it's the same temp or higher in the front the cat is defective.

Didn't we tell him to get one of those a while back for his Buick cooling problem???
 
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