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Cat Converter taking a dump? or Timing way off?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by unsane, Jan 29, 2003.

  1. unsane

    unsane Guest

    Hey guys, my problem is getting out of hand. I am getting like 7-9 MPG on 87 with a brand new motor. Recently the truck starts to shake and stuff like overdrive is going out or like the engine doesnt have enough power to keep a gear, so I have to run it in regular drive. I am getting the black crap out the tail pipe, and the crappy gasmilage to go along with it. The motor is good mechanically though. could this be 1. the 700r4 taking a dump 2. the Cat converter is TACO'd or 3. the timing is all jacked up. I know my diagnosis will be wrong if I dont ask on here first. Where would you start? The shaking and jerking is only at highway speeds also. The gas milage is killing me though, I live 20 miles one way from work and it has been costing close to $40 for a fill-up. Also I am all stock except edelbrock tbi manifold. Thanks in advance for the help. -Eric
     
  2. Thunder

    Thunder 3/4 ton status

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    I would definatly change the cat. Its best to change them after 65000 miles or so.
    But I dont think that is your only problem. Sounds like there are some other issues as well
    definatly check the timing and
    Check the computer to see if there are any trouble codes.
    Could be a bad sensor like the 02 or something
     
  3. tori89k5

    tori89k5 1/2 ton status

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    I see high potential for a couple problems. But i dont know all the details, so i riddle you this:

    perhaps, when you added your Edelbrock manifold, this changed the adjustment of the TV Cable, which over a period of time could have caused damage to the tranny... giving you the shaking, and slippage which may cause your poor MPG..... this.. is just a theory mind you...

    if you still have the factory GM Cat on, and dont mind ruining it if it is still good, you can take a hammer and chisel to the plug in the bottom of it, and open it up. Start up the engine, and drain all the ceramic beads out. Then you will see weather or not it was plugged. You can reseal the CAT after doing this by putting an 1 5/8" freeze plug back in the hole. If you were ambitious, catch all the beads, and put them back in later... You used to be able to get new beads, and may still ???
    Anyway...... just some shade tree ideas to consider. /forums/images/graemlins/cool.gif
     
  4. unsane

    unsane Guest

    I adjusted the TV cable accordingly when I installed the new manifold. This whole thing is just getting on my nerves. escpecialy when my wife just locked up the motor in her 98 grand prix!!! So you can see the $$$$$ money is getting stretched pretty thin about now. Thanks man for the reply
     
  5. tori89k5

    tori89k5 1/2 ton status

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    Thats good news, what about you CAT ? and how come you haven't check the timing if you think thats at issue ?
     
  6. unsane

    unsane Guest

    Well mainly havent done anything with the timing primarily due to 12 hour shifts being a major time consumer for me. I have a plan for the CAT! Its called dissapearing act! /forums/images/graemlins/shocked.gif
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Do the 89's monitor cat converter temp? I would *imagine* that a backed up exhaust from a failed converter would show up as sky high temperatures. I know *sometimes* they will glow red when they have failed.

    I'm assuming you don't have to have emissions tests, so you wouldn't have any clue how effective it is, right?
     
  8. aandpman

    aandpman 1/2 ton status Premium Member

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    I'd check cats /forums/images/graemlins/deal.gif. Mine and my dad's 85's both did exactly the same thing when the cats stopped up.
     

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