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Symptoms of a bad cat converter?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by scott87, Apr 19, 2002.

  1. scott87

    scott87 Registered Member

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    I seem to be loosing power and some gas mileage. Wondering if it is the cat. I still have the original on my truck (about 105,000 miles). What are the symptoms of one being bad, and what are the effects of it?
     
  2. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    i have 153,000 on mine and it is weaker than it should be. i haven't thought about the cat though, mines stock so i bet it could stand be changed.
     
  3. muddysub

    muddysub 1 ton suburban status Staff Member Moderator GMOTM Winner

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    or maybe it's the fact that have 36" TSLs and 3.73 gears? hmmmm...
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Sounds possible. I would reccomend a new cat regardless. Cats have made huge progress in design and flow extremly well. At the least I would recommend bolting in a new high flow cat. Even better would be buying a cat back kit and a new cat.

    You have a throttle body injected motor and I would recommend changing your sensors too as part of a regular matience, like changing your spark plugs. The oxygen sensor I believe is on the driver's side manifold near the bottom of the it. This is what I have seen on '88 truck that I am swaping motors for someone. A new coolant sensor would be good too. It is up on the intake neck to the water neck where the radiator hose exits. It should be to the left of the water neck. A tune-up will help too (plugs, wires, cap, rotor). Try the sensor and tune up before the cat because its a good idea anyways.
     
  5. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    overheating. and that looses power.
    grant
     
  6. Blazinaire

    Blazinaire 1/2 ton status

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    Ocassionally my truck will make a stink like rotten eggs after it has warmed up, is that the cat?
     
  7. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    its the cat but it is not bad. my dads brand new miata makes the same smell from time to time
    grant
     
  8. Thumper

    Thumper 1/2 ton status

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    Ya, my Chevy Lumina car stinks like crazy on the highway especially while I pass another vehicle. Rotten eggs is a perfect description of the smell. Is that a cat? I was really hoping it wasnt the tranny!
    Mike
     
  9. rx7xj

    rx7xj Registered Member

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    A quick way of checking for exhaust restriction is to hook up a vacuum gage and watch you vacuum reading while revving the engine. If the vacuum drops while holding steady 1500 rpm, or if it recovers slowly as you let off the rpms, you probably have a restriction somewhere. The rotten egg smell is from sulfur in the gas, often a problem with cheap gas. Gas refined from Venezuelan crude are often high in sulfur (around here places like Conoco are the worst)
     
  10. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    assume the cat is toast... the catalyst in a cat lasts around 50-75k miles... if yours is the original one, its prolly not doing much of anything related to its original purpose....

    J
     
  11. aandpman

    aandpman 1/2 ton status Premium Member

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    Cat went bad (stopped up) in my TanK10 a couple of years ago. I could hardly climb the hills on the highway on the way to work. Removed that sucker and power CAME BACK INSTANTLY. I've been thinking about building a good high-flow cat single or dual exhaust system for the TanK10. I'd like to get it legal again.
     
  12. white-rhyno

    white-rhyno 1/2 ton status

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    Just crawl under ur rig and hit it with your fist. If it rattles, replace it. Thats another easy way to check.
     
  13. Quack_Addict

    Quack_Addict 1/2 ton status

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    Ditto on the hitting it with your fist test. The tiles inside the converter come loose with age - happened in my `96 Sonoma ZR2. You could hear the cat rattling when you revved the engine. Finally one day the tile came loose one day, rotated 90 degrees inside the cat and plugged it up like a cork. The truck had almost NO power, temp gauge went way up, and the cat made a loud hissing sound.
     
  14. I replaced mine at 172K miles along with a new cat-back system. The old catalytic convertor was toast. It weighed about 30 lbs because the insides were used up. I replaced it with a new high-flow cat convertor. It was a improvement.
     

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