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Z71SIERRA Enthusiast

Z71SIERRA

Posted
Posted

On the way home from work last Friday my 02 5.3 ECSB Z71 Sierra with 63000 miles on it had no power and spark knocked badly when I went out to pass someone. When I drove it though my neighborhood slow it was ok but if you gave it any gas it hardly moved and longer you held the gas down the more the spark knock. If I kept my foot in it for several seconds I get the PO303 spark knock/misfire code. So I spent Saturday changing my fuel filter, cleaning my throttle body, cleaning my MAF (CRC spray mass airflow sensor cleaner is awsome stuff), checking my fuel pressure, checking vacuum, looking for vacuum leaks, putting in fresh gas, Techron fuel system cleaner, ....after a days work...still no power. So Monday I took it in to my GMC dealer and left it to them to diagnose and to take care of my ABS recall. 3 and a half hours later they call and tell me my truck was ready. (Cool.....I hadn't even picked up the rent a car yet!!!) The verdict.....Bad Cat. Has anyone else had to replace their catalytic converters. I find it strange that a truck with 63000 miles that has had nothing but Amoco fuels and Mobil 1 oil its whole life would trash a cat. The good news was that it emission related so it was a freebie! What actually causes a converter to fail?

97chevy350 Enthusiast

97chevy350

Posted
Posted

Really the only thing that causes a cat to fail is it getting plugged with carbon. Have you ever used a top end cleaner through the intake? Even though I am a big fan of the seafoam through the intake, if you have a really carboned up engine, and you clean it out, it can break off large pieces of carbon that will clog the cat. Other than carbon build up or it getting smashed or soemthing that is really all there is to go wrong. All it is is a casing with a honey comb make of materials that reduce the exhause emissions....

Z71SIERRA Enthusiast

Z71SIERRA

Posted
  • Author
Posted

I've never run a top end cleaner through it but I do clean the throttle body every 4th oil change and run a bottle of Techron fuel system cleaner through every other. I was hoping good preventative maintainance would keep me from needing a top end cleaning. I run the freeway back and forth to work and I don't idle much. Do you think I still build up carbon? I had a 93 Sonoma with an HO 4.3 that I maintained the same way and never had problem up til I sold it with 160,000 miles on it.

97chevy350 Enthusiast

97chevy350

Posted
Posted

With mostly highway miles and you keeping up on it (techron is a very good cleaner), i really cant see it being clogged with 63,000 miles on it, but other than the honeycomb inside being busted, thats really all that can go wrong, there are no moving parts or anything, its essentially just a big (expensive) filter. They used to have platinum in them but they are getting away from that because people were stealing them....

Rolandd Enthusiast

Rolandd

Posted
Posted

If the cat overheats the honeycomb can melt causing it to plug without carbon build up. Many things can cause the cat to overheat depending on how you drive (highway vs city, loaded vs unloaded, etc.). It might be worth asking the dealer what they think so that you can modify your use habits if needed so that the next cat is not on you.

mxzeatr Enthusiast

mxzeatr

Posted
Posted

Shouldn't your cat be under warrenty still? I thought I remember reading that the cats are covered long after the actually warrenty of the truck runs out. My truck has a cat failure right now, I have not noticed any loss of power, the code says 'catalyst efficency below threshold' meaning that one of the cats isn't functioning properly. I have been gettting decent fuel milage and it hasn't been running too bad, so I am hoping to make it thru the end of the school year til I start work again....My truck is a 99 and it has 139xxx miles on it...I think mine is just old and clogged...But with less then half the mileage maybe your cat wasn't manufatured properly or something...

dewfpo Senior Enthusiast

dewfpo

Posted
Posted

Too rich a mixture, misfires, can cause the cat to overheat, melt, then collapse on itself causing a blockage.

 

DEWFPO

david.mciver Enthusiast

david.mciver

Posted
Posted

I have not had the issue with a Chevrolet but did have a CAT failure on a 2001 Jeep Wrangler when it was 3 years old with only 40K miles on it... Never had any other issue with the Jeep up until the time I traded it so I chocked it up to being due to a defective component. In the case of the Jeep it was covered by an extended warranty which I believe we out to 60K miles. The other odd thing is there was no performance degradation due to the CAT failure. The only indication I had was a service engine soon light which when read stated bad CAT.

  • 5 months later...
chev9644 Enthusiast

chev9644

Posted
Posted

My 96 K1500 silverado 5.7 Vortec keeps giving me a code "P0430 = Catalyst Efficiency Below Threshold (Bank 2)". I've replaced the O2 sensors fairly recently so i don't think that is the problem. This truck has 163,000 miles and the catalytic convertors have never been replaced. Does that sound like the problem and if so is there a fairly cheap universal replacement for both catalytic convertors? I know the factory set up with pipes to the manifolds is $300-$500 so i'd rather cut out the old cats and weld in new ones if possible. It also has a "P1403 code = EGR valve pintle position" could this be causing the P0430 code to happen?

Sly Enthusiast

Sly

Posted
Posted
On the way home from work last Friday my 02 5.3 ECSB Z71 Sierra with 63000 miles on it had no power and spark knocked badly when I went out to pass someone. When I drove it though my neighborhood slow it was ok but if you gave it any gas it hardly moved and longer you held the gas down the more the spark knock. If I kept my foot in it for several seconds I get the PO303 spark knock/misfire code. So I spent Saturday changing my fuel filter, cleaning my throttle body, cleaning my MAF (CRC spray mass airflow sensor cleaner is awsome stuff), checking my fuel pressure, checking vacuum, looking for vacuum leaks, putting in fresh gas, Techron fuel system cleaner, ....after a days work...still no power. So Monday I took it in to my GMC dealer and left it to them to diagnose and to take care of my ABS recall. 3 and a half hours later they call and tell me my truck was ready. (Cool.....I hadn't even picked up the rent a car yet!!!) The verdict.....Bad Cat. Has anyone else had to replace their catalytic converters. I find it strange that a truck with 63000 miles that has had nothing but Amoco fuels and Mobil 1 oil its whole life would trash a cat. The good news was that it emission related so it was a freebie! What actually causes a converter to fail?

 

Had one fail on my Denali. Alot of factors can affect why it failed. Probably running rich.

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