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Thread: P0304

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    VIP Member GXPaycheck's Avatar
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    Default P0304

    Soooo, I was out playing around in GXP 715 and when I hit 5k she started running rough and up popped the check engine light. Quick check showed P0304. Car idles fin but gets rough when trying to accelerate. My plan is to replace plugs and wires (the original ones are still in) and see if that fixes it. Any suggestions are welcome!
    RIP Charlie, The GRRRR8 One


    [SIZE="2"][COLOR="Red"]

    2009 G8 GXP, #715 0f 1829 (one of 38 as optioned), MSM, M6, Sunroof, Onyx/Red
    2009 G8 GXP, #807 of 1829, MSM, A6, sunroof
    2016 Chevy SS, Mystic Green, roof, spare, #555 of 2221.




    You can push the envelope, but it's still stationery

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    Moderator, Retired -Ray-'s Avatar
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    Swap coils with another cylinder prior to changing all that.
    Rest in Peace Charlie!

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    Quote Originally Posted by RichsGreyGT View Post
    this site is hardcore modding central.

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    So that's what mine did under the exact same scenario. Do all the free and simple trouble shooting and then go do a leak down test. You may also want to pull the valve covers to make sure you didn't break a valve spring. Mine had over a 40% leakdown in one of the cylinders so I pulled the motor. I am still not exactly sure what's wrong with it but I did find a big chunk of metal in the pan along with a lot of grey metallic goop. So it was eating something. In my case it was not the heads nor the #8 piston (all the rings are intact) which had a severe leak down. I have stopped trying to figure out exactly what has failed, I will leave it to the machine shop to figure it out.

    Good luck and I hope it's something simple but be prepared for it to be something not so nice.
    69Project
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    Beyond Help todds87ss's Avatar
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    Quote Originally Posted by 69project View Post
    So that's what mine did under the exact same scenario. Do all the free and simple trouble shooting and then go do a leak down test. You may also want to pull the valve covers to make sure you didn't break a valve spring.
    My thoughts also. If the coils check out, I would use an IR temp gun to check each exhaust port. Any low numbers - pull that Valve Cover and check the springs.
    Yes for us larger guys that screw can be a pain!

    08 G8 GT, IOM, Rotofab, HSRK, Kooks LTs, track pipes, Custom engine covers, catch can, radiator cover, and tranny tunnel brace. 402hp/396tq - not bad for a bolt -on car.
    8.43 1/8th; 2.01 60' - no skillz.

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    VIP Member GXPaycheck's Avatar
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    Think I might've found the problem

    plugs.jpg
    RIP Charlie, The GRRRR8 One


    [SIZE="2"][COLOR="Red"]

    2009 G8 GXP, #715 0f 1829 (one of 38 as optioned), MSM, M6, Sunroof, Onyx/Red
    2009 G8 GXP, #807 of 1829, MSM, A6, sunroof
    2016 Chevy SS, Mystic Green, roof, spare, #555 of 2221.




    You can push the envelope, but it's still stationery

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    So, how many miles on those plugs?

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    VIP Member GXPaycheck's Avatar
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    70k
    RIP Charlie, The GRRRR8 One


    [SIZE="2"][COLOR="Red"]

    2009 G8 GXP, #715 0f 1829 (one of 38 as optioned), MSM, M6, Sunroof, Onyx/Red
    2009 G8 GXP, #807 of 1829, MSM, A6, sunroof
    2016 Chevy SS, Mystic Green, roof, spare, #555 of 2221.




    You can push the envelope, but it's still stationery

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    Moderator, Retired -Ray-'s Avatar
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    Quote Originally Posted by GXPaycheck View Post
    Think I might've found the problem

    plugs.jpg
    No, that's the symptom. Looks like pre-ignition to me. Is the car tuned? If it's not, I'd want to get an inspection camera and get a look at the top of a piston or two.
    Rest in Peace Charlie!

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    Quote Originally Posted by RichsGreyGT View Post
    this site is hardcore modding central.

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    Good point Ray. Was wondering how the plugs would get so messed up.

  10. #10
    VIP Member GXPaycheck's Avatar
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    Quote Originally Posted by -Ray- View Post
    No, that's the symptom. Looks like pre-ignition to me. Is the car tuned? If it's not, I'd want to get an inspection camera and get a look at the top of a piston or two.
    That had occurred to me. Car is not tuned, just intake and exhaust. I just filled the gas tank and was wondering if bad gas could’ve caused it. I have an inspection camera that will fit in a plug hole. Have to add that to my list of things to do
    RIP Charlie, The GRRRR8 One


    [SIZE="2"][COLOR="Red"]

    2009 G8 GXP, #715 0f 1829 (one of 38 as optioned), MSM, M6, Sunroof, Onyx/Red
    2009 G8 GXP, #807 of 1829, MSM, A6, sunroof
    2016 Chevy SS, Mystic Green, roof, spare, #555 of 2221.




    You can push the envelope, but it's still stationery

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