1996 Suburban K1500 check engine question

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by barryT, Feb 21, 2010.

  1. barryT

    barryT Member

    My check engine light is on and I have read the codes. It is say low catalytic converter efficiency. Also my mileage seems to have gone down hill recently. Should I replace the cats or could this be caused my something else. My suburban is a 5.7 vortec 4x4 with 168,000 miles. Second question. How and when do I know to replace the EGR?

    Thanks ahead of time,

    BASSIST Rockstar 100 Posts

    Have the cats checked. The EGR will throw a different code
  3. barryT

    barryT Member

    They are cheap enough to replace, so I might order them today. I replaced the o2 sensors and then they said the cats weren't working correctly.

  4. barryT

    barryT Member

    My only question is don't cats pretty much last forever? My plugs look good and there isnt anything wrong with my ignition system. The o2 sensors on the left bank are new and the right bank 02 sensors are original. Could it be throwing off a check engine light because the 2 sides are reading differently? Should I try new right side o2 sensors first?

  5. Gambit

    Gambit Rockstar 100 Posts

    Once again that would be a different code. Yes generally Cats will last the life of the vehicle however they are known to fail. Many different thngs could lead to the failure of a Cat. If the code is saying it is in the Cat you can assume that the cat is the issue. If you dont want to just spend money on a new one take it to an exhaust shop and have them look at it to see if it is bad and if possible what made it go bad.
  6. barryT

    barryT Member

    Well I bought two new oxygen sensors for the right hand side and I bought a new bolt in magnaflow cat system. The only problem is the bolts going from the the cats to the exhaust manifold are insanely tight. One of them unscrewed the stud instead of the nut witch is fine, and the one next to it just stripped half the stud threads on its way out. I stopped the project there and have been trying to remove/fix that stud since. I tried craftsman bolt out to remove the stud with out an luck. Now I am going to try to run a bolt threard restorer down the stud to fix the last bit of threads so I can get a bolt on it. I never did get the exhaust off. I am going to wait till next week when I can take it down to the base shop and put it on a lift and have some room. I did in the mean time use a mid sized c-clamp to hold the flange together where the nut is supposed to be. I also safety wired it so if it comes fly off it wont destroy anything. For now I dont have any exhaust leaks and the c-clamp seems to be working well.
    Last edited: Mar 4, 2010
  7. barryT

    barryT Member

    Well I was able to get the thread restoring die down the stud and clean up the threads enough to fit a nut and get it torqued down enough to seal the exhaust properly. I am going to be soaking the Nuts and the studs in liquid wrench for a few days and tackle the job on Tuesday. I was able to put the new oxygen sensors fitted on the right bank though. The idle is better and my acceleration with light pedal pressure seems better. I am assuming my gas mileage will get better. The oxygen sensors I pulled out were the originals. 168K on them.

  8. barryT

    barryT Member

    I was able to get the cats installed with the help of a 3 ft breaker bar at the shop on base. Everything seems to be going well and the gas mileage seems to be better. I dont hear any exhaust leaks and I have had a few people listen to make sure. The bad news is my wife just called and said the check engine light just came on again. If it low cat eff code again Im going to be pissed off. If its still bank one I'm going to switch oxygen sensors and see if the code follows. Maybe the one of the back sensors is mulfunctioning. I guess I wont know till I read the codes on tuesday.

  9. barryT

    barryT Member

    Well its been a couple weeks now and everything is going pretty well. I did get another check engine light, but it ended up being an oxygen sensor. I hit with a wrench on accident and thought it was ok, but it apparently wasnt. The oxygen sensor was brand new, but still got stripped on the way out. I had to get a O2 thread chaser from sears witch fixed my issue quickly. Now the burb runs great. It did sound like it was leaking exhaust but only for a second then it went away. I bought new exhaust donuts anyway and will be doing them in a couple weeks. With 4 new injectors and new magna flow cats my gas mileage has gotten a little bit better and thats a great thing these days.
  10. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    Glad you got it chased down... and have fun with the exhaust donuts well here in MN it basically means your gonna be pulling exhaust manifolds... The bolts basically desinigrate....

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