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Inconsistant Engine Performance

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jc71355, Nov 21, 2002.

  1. jc71355

    jc71355 1/2 ton status

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    The engine in my 91 is very inconsistant. Sometimes it runs good sometimes it runs bad. Sometimes it has lots of power someimes it's a DOG! I'm saving up for a scanner and I just ordered Header Hush to keep my collectors sealed up. Even when the collector's aren't leaking the engine doesn't allways run good. The engine will not have any power and will vibrate the floor. Could this be a worn out Throttle Body? My engine is Rapidly approaching 200k miles and I'm wondering if the injectors and such are wearing out. Any Opinions? /forums/images/graemlins/1zhelp.gif

    TIA
    James
     
  2. Highlander

    Highlander 1/2 ton status

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    Have you done a compresion and leak down test yet? What about a your cat's? next thing I would say is to look for a vacuum leak. Sorry I can't be of more help

    Eric
     
  3. jc71355

    jc71355 1/2 ton status

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    I haven't done a Comp. Test yet. I looked for cracked or leaking vacuum lines and didn't find any. The Throttle body is bolted down tight. I do occasionally get a hissing sound from the engine. I can't find where it's coming from or anything because it only does it when i'm moving. I kinda assumed it might be my collectors but I can't tell if it's sucking in or blowing out.
     
  4. Highlander

    Highlander 1/2 ton status

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    I would think if it was the collectors it would be blowing out
    But hissing only when your moving is weird. I would think you would still beable to hear it even if you rev'd up the motor so you could hear it better.
    is your Check eng. light coming on?

    Eric
     
  5. jc71355

    jc71355 1/2 ton status

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    Yea Code 44. My 02 Sensor is behind my collector though...
     
  6. Highlander

    Highlander 1/2 ton status

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    I take it you read what it says in the Manual?
    Lean exhaust: Probable cause; check the wires from the ESC mod to the ECM. Have the fuel pressure checked. Check the O2 wire. Check the carb or TBI gasket vacuum hoses and intake gaskets for leaks. and lastly replace the O2 sensor.
    Sometime ago I had a Holly Pro-Jection on a 400sbc sometimes I would get vacuum leaks under the throttle body.
    Get your self a vacuum gauge and see what it says.

    Eric
     
  7. jc71355

    jc71355 1/2 ton status

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    Can a vacuum guage tell me If I'm leaking under the TBI?
     
  8. jc71355

    jc71355 1/2 ton status

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    I just cranked her up and let her run for a minute and then hosed every vacuum hose and the Throttle body with WD-40 and I didn't get any rpm change. I even revved it up to see if I could get it to hiss but I couldn't.
     
  9. Highlander

    Highlander 1/2 ton status

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    No, But it will tell you if you have a vacuum problem like a sticking valves and such. Over all the tool it self is a big help when you do a tune up.
    The other thing you could try is useing a UN-lit propane torch with you motor running take the torch and put by you vacuum lines and you intake just keep it away from the air intake for the TBI. As you do this if the motor picks up in Idle you found your leak. run it around the intake and TBI gaskets.
    Of corse I could be way off base.
    By the way how are your cats? does your exhaust sound off?
    Well I don't know what else to say if the WD-40 didn't turn up a leak
    How about a calling a Preist and have him bless it? /forums/images/graemlins/smile.gif
     
  10. jc71355

    jc71355 1/2 ton status

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    Humm... I never thought of a priest /forums/images/graemlins/rotfl.gif. I don't have any cat's, just true duals w/flows.
     
  11. jc71355

    jc71355 1/2 ton status

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    Ok new question. How do I know when my injectors or pressure regulator are messing up?
     

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