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Crap 5.7?

Discussion in 'The Garage' started by PsychoticDeadGuy, Jun 12, 2006.

  1. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    Well, on my way to go wheeling yesterday, my motor started missing and running really rich, and on startup, it surges a few time then get to a missing 700ish RPMs. What could cause this? Bad plugs, wires, cap and rotor? What about o2 sensor for the running rich?
     
  2. richheezee

    richheezee 1/2 ton status

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    vacuum leak.
     
  3. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    Well, I just replaced the o2, plugs, wires, cap, rotor, and the air filter. It still surges but not as bad. It also spits out black smoke, what does black mean?
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    black smoke is running rich.

    did you change the ignition module?
     
  5. sled_dog

    sled_dog 1 ton status

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    it would run lean if there were a vacuum leak...

    can you give a little background on your rig? headers with a standard one wire O2? tbi? anything changed recently?
     
  6. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    my rig ran pefectly fine, it just happened. the plugs and o2 sensor were charcoal black, not oily. the motor is all stock, TBI. could it be the timing?
     
  7. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Check your coolant temp sensor, MAP sensor, and 02 sensor -- In that order.

    They are the three components that control your fuel the most :)
     
  8. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    I already changed the o2 sensor. How does the MAP and temp sensor affect the motor to make it sound like its missing and blowing out black smoke?
     
  9. sled_dog

    sled_dog 1 ton status

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    if its running as rich as it needs to be to blow black smoke its going to misfire on fuel.

    MAP and ECT are 2 of the 3 primary inputs in a TBI system. The computer uses their input A LOT to determine how much fuel to put it. The MAP lets it know how much fuel is coming in, and the ECT lets it know how cold the engine is.
     
  10. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

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    Is it not throwing any codes???
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    My guess is either the vacuum line came off the MAP sensor or is plugged or the MAP sensor is just plain bad. I had my rig run the same way once when the vacuum line came off the MAP sensor.
     

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