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crazy engine bogging... 350 TBI

Discussion in '1973-1991 K5 | Suburban | Truck' started by FlatBlackBurb, Sep 24, 2007.

  1. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    okay so in my 87 chevy suburban with a 5.7 TBI, when im going up a steep hill or basically any hill... the engine boggs reallly bad. it only happens when the engine is at half on the temp gauge. at first there is a considerably loss of power, and i have to put my foot down even harder, and then it makes a ticking sound, almost like the sound of someone tapping on a muffler with a stick. and then the bogging starts. the engine backfires like crazy and almost dies. theres a huge loss of power and accelleration stops all together. the problems i mentioned here seem to be minimized when im crawling at like 5mph... but id rather get to the good part of a trail quicker than that.. its been doing this for a while, im going to get new spark plugs and see if that does anything... my spark plugs are fairly new though.


    recent parts:

    MAP sensor
    ignition module
    plug wires
    fuel filter
    fuel pump
    starter
     
  2. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    Does it throw any codes?
     
  3. loafer

    loafer 1/2 ton status

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    Sounds like a fuel problem to me.

    My 88 used to do that when the fuel filter would plug up.
     
  4. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    it did throw a code when i changed all of those parts out, only because one of the cables that goes into the MAP sensor wasnt in there all the way. now it doesnt throw any. and i just replaced the fuel filter too! could it be a spark plug problem? im going to get new codes today and see what happens.
     
  5. Rob 85K5

    Rob 85K5 1/2 ton status GMOTM Winner

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    Is the tranny downshifting??
     
  6. mxfireman

    mxfireman 1/2 ton status

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    I know this sounds a little crazy buy my K5 that is carbeurated started doing the same thing and it took my a whole year to figure it out. It was my catalytic convertor getting plugged up due to a header deteorating from the inside out. It is very easy for a exhaust shop to check it out.
     
  7. newlyblzed

    newlyblzed 1/2 ton status

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    if you can you might want to do a fuel pressure check...although I don't see it failing only when going up a hill...thats usually a carb issue not TBI. sounds like it should be throwin some definate codes.
     
  8. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    yeah i think im gonna take a look at the cat. i was just gonna cut the thing off anyway maybe that will fix things.
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    If you've got a pressure gauge, you can test the cat converter, tap the gauge in front of the cat, should be less than 5PSI with some throttle IIRC. I think some of the new stuff is 3PSI, but if it's plugged up, it's probably a higher number. Lot easier and responsible than removing a potentially working part. If the pressure isn't high, it isn't hurting performance.

    You might also do the same test on your muffler, no reason it couldn't be screwed up, and a waste of time to blame the converter if the muffler is bad. Could be that the converter came apart and is plugging the exhaust up further downstream, etc.

    Since it's this consistent, and pops through the TBI, at this point I'm leaning away from something electrical like fuel delivery, etc., although any cause that limits power based on engine load should likely be repeatable even on hard, prolonged acceleration on flat ground.

    No difference if the tank is completely full or not? Problem subsides if you let off the gas?
     
  10. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    no difference at all if i have a full tank or not. it does a little bit of bogging on flat surfaces but its mostly noticably uphill.... i think im just gonna gut the whole thing and weld on the muffler with exhaust dump after the manifolds.
     
  11. mxfireman

    mxfireman 1/2 ton status

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    Mine is gone along with all the smog junk.
     
  12. dinkster

    dinkster Registered Member

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    A friend of mine had a car with similar symptoms, and it was the cat too. I agree with the cat theory.
     
  13. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    anyone in northern california wanna help me weld on the muffler?
     
  14. G-Force8

    G-Force8 1/2 ton status

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    have you checked the Throttle Position Sensor?
     
  15. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    no i havn't yet. where is it located exactly? ive heard they arent adjustable and then ive heard they are. should i get an aftermarket replacement from autozone or something?
     
  16. redbeast24740

    redbeast24740 1/2 ton status

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    That sensor is on the right side of the tbi.Its none adjustable. Also i had the same problem it was the cat clogged. Except i found out the hard way and replaced about every electronic part on the engine before i got to that. I was searching forms like crazy about it and had several different items that were causing the same problem.
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    You can test the TPS.

    This is another of those Delco or nothing parts IMO, and not one I would replace in hopes of fixing a problem. Way better off buying tools than blindly buying parts.
     
  18. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    What you have described sounds like you are having a detonation issue. Have you checked your timing yet? You will need to disconnect the tan wire near the brake booster before checking timing and the timing should be TDC or zero if you will.
     
  19. FlatBlackBurb

    FlatBlackBurb 1/2 ton status

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    yeah timing is fine. im gutting the cat. no questions asked

    :hack:
     

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