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Bad catalytic converter??????

Coloradochevyguy91

Coloradochevyguy91

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Ok I'm pretty sure my cat is plugged but before I delete it I want to make sure. So I'll start with the truck it's a 1991 Chevy k1500 350 tbi 700r4 with god knows how many miles ( odometer gears broke years ago ). Recent tune up ac delco plugs copper, msd wires, brand new distributor all new sensors. Engine oil level good, trans fluid good and not burned. I replace the o2 sensor last night and the coolant temperature sensor and maf.
Now on to the symptoms...
When pulling a hill engine bogs down I shift it out of overdrive the rpm's race up but no real difference in speed. My fuel economy has dropped a ton. My exhaust seems quiter than normal I crawled under it banged on the cat with a hammer I can hear metal inside the cat banging around. And sometimes the trans will not up shift till I let completely off the throttle. I drive it this morning with out shifting problems.
I forgot to mention it does have a cat back exhaust I think it has a magnaflow hi flow cat and I know for sure a flowmaster 40 series muffler.
All advise is helpful my truck is registered in a non emission county so I really don't need the cat.
 
You can pull the oxygen sensor and put a pressure gauge there. A vacuum gauge on the intake can also tell you something. A bad exhaust restriction will reduce the vacuum. You need some idea of what it normally would be, though. I've seen a cat almost entirely plugged - when the engine first starts it makes good vacuum and then the vacuum drops steadily until the motor chokes out and dies.

Isn't there a connector someplace you could take apart - after the crossover pipe or something? Just to see if the truck runs better before hacking the cat out. No cat is smelly.
 
Blue85 said:
You can pull the oxygen sensor and put a pressure gauge there. A vacuum gauge on the intake can also tell you something. A bad exhaust restriction will reduce the vacuum. You need some idea of what it normally would be, though. I've seen a cat almost entirely plugged - when the engine first starts it makes good vacuum and then the vacuum drops steadily until the motor chokes out and dies.

Isn't there a connector someplace you could take apart - after the crossover pipe or something? Just to see if the truck runs better before hacking the cat out. No cat is smelly.
Click to expand...
No it's fully welded. The only place it where the y pipe bolts the exhaust manifold and yes the exhaust smells like rotten eggs...
 
My friend at his repair shop often just removes the O2 sensor and goes for test ride--usually if the converter was plugged up,it'll run much better--some cars towed in wouldn't even start until the O2 sensor was removed,they were blocked up so bad!...its easier than taking the cat off completely..
 
Eh, it's good for a couple hundred thousand more miles...

Nothing like 100HP and 5MPG for a couple hours work.
 
I would have cashed it in for scrap and welded or clamped a pipe in its place,if its not a must to pass inspection in your area...
Some converters are not worth much though ..
 
diesel4me said:
I would have cashed it in for scrap and welded or clamped a pipe in its place,if its not a must to pass inspection in your area...
Some converters are not worth much though ..
Click to expand...
We thought about it but getting around to doing it when Budweiser is involved is a completely different problem haha.
 
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