1995 5.7 TBI Sputtering and Backfiring

Discussion in 'GMC Truck Forum' started by tim301, Jan 28, 2012.

  1. tim301

    tim301 Member

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    [TD="width: 100%"]Hi Folks,

    My 95 yukon started backfiring when I do a moderate acceleration. It's a 5.7L gas engine. This condition started abruptly, it was not something that slowly got worse.

    It does not seem to do any backfiring/sputtering until it warms up. Cold seems ok.

    Thinking that it was ignition related (losing spark & extra gas dumped in the TBI), I replaced all 3 of the ignition related parts. Reset the timing to 3deg, and it starts fine (it always did tho).

    But, it still sputters and backfires a lot. I've noticed that the tach will 'flutter' driving 'normally', but will really move around when it backfires. Almost like it's losing spark.

    I've checked all of the vacuum hoses, and all are solid (replaced a couple). Also replaced the O2 sensor (it's got 245k miles on it & never replaced).

    I have not replaced the fuel filter, and <really> don't want to replace the fuel pump. (just did that on my 94 yukon). ugh.

    I have run an additional tank of gas through it, used some 'gas additive', and have sprayed down the TBI with carb cleaner.

    Any ideas or comments would be appreciated.

    Thanks,

    Tim


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  2. dirtrider73068

    dirtrider73068 Moderator Staff Member

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    Is the check engine light on? If so most auto part stores will check it for free see what if any codes it has.
     
  3. chevychase

    chevychase Senior Moderator Staff Member

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    When you say you change ignition related what were they? Will wait on check light as dr. advised...and parts changed.
    Before saying anything else .
     
  4. tim301

    tim301 Member

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    No engine lights, replaced the ignition coil, the pickup coil, ignition module, distributor cap & rotor.

    Will take it into town on Monday to see if any codes were thrown. (can you have codes without an engine light)?

    Tim
     
  5. dirtrider73068

    dirtrider73068 Moderator Staff Member

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    If the light has come on before yes there can be codes stored once the light comes on. Did you change the wires and plugs to as well.
     
  6. chevychase

    chevychase Senior Moderator Staff Member

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    Need to check filter ..fuel pressure 9 to 14 psi.
    Also could be map sensor. Was thinking pickup but you changed that.
    Change the coolant temp sensor located beside thermostat housing..ten bucks .
    something showing up when ecm goes closed loop...hence runs good cold.
     
  7. tim301

    tim301 Member

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    No, I didn't change the wires or plugs.. figured it was something more catastrophic!
     
  8. dirtrider73068

    dirtrider73068 Moderator Staff Member

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    Could be that simple, need to pull the plugs look at them see if what kind of shape they are in, plug wires break down get weak, create resistance over time reduces spark.
     
  9. chevychase

    chevychase Senior Moderator Staff Member

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    Did you pull bed or drop tank on 94? When changed pump.
     
  10. dirtrider73068

    dirtrider73068 Moderator Staff Member

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    It was a yukon CC they don't have beds :)
     

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