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Thread: The p0300 fun code 2000 Yukon 5.3

  1. #1
    Forum Member lone racer's Avatar
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    Default The p0300 fun code 2000 Yukon 5.3

    Starts a little rough, quick stumble and then idle first try when cold and gets worse when warm ,meaning up to three attempts of stumble and stall or extended stumble and finally raise to idle WITH noticeable miss at idle at any temp. No off idle/drivability issues, smooth throttle response.
    Plugs and wires are new
    Fuel filter= OK
    Fuel pressure @50 spec calls for 55-60 ish
    carb cleaner vacuume leak check= NO Leak found

    I just got a hf special centech scan tool 60794 w/lsd and playback, but I have never used any scanner so the info might be there but I donít know what the values should look like anyway.

    Just give me the fix and problem solved is the ideal situation But.....
    Seriously if you have ANY helpful pointers or suggestions where specific info can be found I would appreciate any positive direction.

  2. #2
    Club Member Beigg's Avatar
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    Can you do an injector balance test? Might have an injector problem.

  3. #3
    Club Member dave89iroc's Avatar
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    check for a leaking FPR as well
    ASE Master Certified Technician

  4. #4
    Forum Member lone racer's Avatar
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    Beigg,

    No, I assume a special tool is needed.
    Last edited by lone racer; 10-11-2017 at 08:20 AM.

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    Forum Member lone racer's Avatar
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    I did pull the vacuum line off of the regulator and a steady dribble coming from the reg. Hopefully that fixes hard starting BUT will it cause p0300 ? A -5 psi difference in pressure causing the random miss ? Possible but that’s way too easy. I will let you guys know what happens.
    Have to run some errands then replace it and go from there.

  6. #6
    Club Member dave89iroc's Avatar
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    Quote Originally Posted by lone racer View Post
    I did pull the vacuum line off of the regulator and a steady dribble coming from the reg. Hopefully that fixes hard starting BUT will it cause p0300 ? A -5 psi difference in pressure causing the random miss ? Possible but that’s way too easy. I will let you guys know what happens.
    Have to run some errands then replace it and go from there.
    I've seen wierd issues from it

    have you looked at the spark plugs lately?
    ASE Master Certified Technician

  7. #7
    Forum Member lone racer's Avatar
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    just replaced them and wires the other day only because previous owner bought them and threw them in the back because he got sick and tired of trying to fix this gem.

  8. #8
    Club Member WhiteHawk's Avatar
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    I would look for a cracked spark plug. Sometimes just the ceramic will micro crack and you can barely see it. I had that on my old 99 Camaro once and was told by my mechanic "That's why we buy top of the line spark plug sockets". I looked, mine was an old piece of crap that didn't even have the rubber boot anymore.

    -Geoff
    2016 Camaro Convertible 2SS

  9. #9
    Club Member Beigg's Avatar
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    Quote Originally Posted by lone racer View Post
    I did pull the vacuum line off of the regulator and a steady dribble coming from the reg. Hopefully that fixes hard starting BUT will it cause p0300 ? A -5 psi difference in pressure causing the random miss ? Possible but that’s way too easy. I will let you guys know what happens.
    Have to run some errands then replace it and go from there.
    Regulator should not allow fuel to secrete in to the vacuum line. Replace the FPR and associated o-rings.

  10. #10
    Forum Member lone racer's Avatar
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    All hail the mighty MM has done the impossible!
    If you ask - theyyyy answer
    They are not only Gentlemen
    They are ......... idk, smarter than the average bear!
    In my book “ The mighty p0300 slayer “
    I should go on for days but I gotta go �� .

    Thanks guys

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