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  1. #1
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    Default HELP ME cylindar 6 misfire

    I have a flashing ses and it brings up p0306 misfire cylinder 6 ive put new spark plugs and wires checked the coil packs and fuel injectors still have misfire p0306 I have backfireing low exceleratiom high knock plz any help would be great thanks in advance I have a 2005 gp gtp

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    GTP Level Member cheatah faheatah's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Move the coil packs to see if misfire follows it.
    not what it looks like

  3. #3
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    Default Re: HELP ME cylindar 6 misfire

    ^ yep. that would definitely be the first step. Next I would double check to make sure that the firing order is correct. Do a compression check. A bad ICM may cause this issue. pull the harness and check for corrosion and damaged pins.
    2007 Grand Prix GT. Pacesetter headers, 1.8 roller rockers, CAI, HPTuned, 3.4pulley, TEP transmission, fuel pump and alt rewire, poly mounts/performance suspension, Impala front brakes drilled and slotted rotors.
    Past Grand Prix- 97 GT, 03 GT, 04 GT, 04 Comp G.

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    SE Level Member wstefan20's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    If the misfire doesn't move with it, I'd put a long handled screwdriver to the injector and put your ear to the butt of the screwdriver to listen for the fuel injector actually actuating. If you hear it clicking, I'd do compression test followed by leakdown test if compression is good. I hope for your sake that it isn't anything major! Good luck

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    Default Re: HELP ME cylindar 6 misfire

    Do you have any smoke coming out the tail pipe? By the sounds of it, your problem is internal. I'm betting broken spring or a failed lifter.

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    Default Re: HELP ME cylindar 6 misfire

    I did check the injectors there good and changed coil packs around still says it #6 I will try to get a compression test done today I'm not sure about smoke oput of tail pipe I will have to check. I hope its not a lifter or broken spring but if it is then I guess I will just get zzp 1.9 rockers

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    SE Level Member davids06gp's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by Toocidnab View Post
    I have a flashing ses and it brings up p0306 misfire cylinder 6 ive put new spark plugs and wires checked the coil packs and fuel injectors still have misfire p0306 I have backfireing low exceleratiom high knock plz any help would be great thanks in advance I have a 2005 gp gtp
    I have a similar issue. I service engine soon light is on, there is a misfire on the number 5 cylinder with tapping and engine vibration. There is no smoke from the tail pipe and I still have good power. I replaced all the coil packs, wires, spark plugs and the ignition control module. I either have lifter issues or a bad fuel injector. I plan to examine the fuel injector soon. Good luck with your misfire issue.
    Last edited by davids06gp; 6 Days Ago at 08:37 AM.

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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by davids06gp View Post
    I have a similar issue. I service engine soon light is on, there is a misfire on the number 5 cylinder with tapping and engine vibration. There is no smoke from the tail pipe and I still have good power. I replaced all the coil packs, wires, spark plugs and the ignition control module. I either have lifter issues or a bad fuel injector. I plan to examine the fuel injector soon. Good luck with your misfire issue.
    Did a compression test they all are 125 or 130 im stuck think maybe a spring or lifter problem

    Sent from my LGMS550 using Tapatalk

  9. #9
    SE Level Member GrandPrixGT1's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by waupachino View Post
    Do you have any smoke coming out the tail pipe? By the sounds of it, your problem is internal. I'm betting broken spring or a failed lifter.
    Youíd be able to hear a broken lifter and I donít recall that he said hearing anything. I maybe wrong though. The broken spring is probably a good possibility because then heís not getting air or fuel. I donít think youíd be able to hear that one.

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    Default Re: HELP ME cylindar 6 misfire

    Would u be able to see that the spring is broken with just taking the Vaulve cover off

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    SE Level Member GrandPrixGT1's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by Toocidnab View Post
    Would u be able to see that the spring is broken with just taking the Vaulve cover off
    Yes you should be able to. Did you check the injector? I know you said you did new plug wire and coil pack.

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    SE Level Member GrandPrixGT1's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by GrandPrixGT1 View Post
    Yes you should be able to. Did you check the injector? I know you said you did new plug wire and coil pack.
    Sorry I didnít read it fully. So your getting air and fuel. Have tried pulling the plug out and testing it to see if itís giving spark?

  13. #13
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    Default Re: HELP ME cylindar 6 misfire

    The spring won't be broken and the lifter won't be bad if you are getting good compression. If the spring broke, the valve would be open.

    Do you have an exhaust leak?
    What fuel do you run?
    If you know anyone with a borescope, it's time to look inside the cylinder at the piston. You may have chipped the landing.

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    SE Level Member GrandPrixGT1's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by BillBooost37 View Post
    The spring won't be broken and the lifter won't be bad if you are getting good compression. If the spring broke, the valve would be open.

    Do you have an exhaust leak?
    What fuel do you run?
    If you know anyone with a borescope, it's time to look inside the cylinder at the piston. You may have chipped the landing.
    If itís chipped I donít think heíd be getting good compression. Piston rings are good then as well. If it was chipped bad enough to break the seal on the piston and cylinder wall heíd definitely know it and would be burning a good bit of oil.

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    Default Re: HELP ME cylindar 6 misfire

    Quote Originally Posted by GrandPrixGT1 View Post
    You’d be able to hear a broken lifter and I don’t recall that he said hearing anything. I maybe wrong though. The broken spring is probably a good possibility because then he’s not getting air or fuel. I don’t think you’d be able to hear that one.
    Not always true. In my case the whole roller broke completely off and the body of the lifter was hanging in the lifter bore. No noise, because there was no movement of the lifter. Also if it's the exhaust lifter that's not moving, it would still make compression.

  16. #16
    GT Level Member Gregorius's Avatar
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    Default Re: HELP ME cylindar 6 misfire

    Huh. No one has suggested coolant/oil into the cylinder fouling the plug? LIMs done? That being said, It's awfully easy to mix up the plug wires, after fixing a bad plug. Hell. I do most of time, it seems.

    More info! Always dead cylinder? Does it gets better after it warms up?, starts missing after it warms up? Idle ok? Only flashes after partial throttle? Half throttle? WOT? Starts flashing as soon it's started? and then only when cold? Only after it warms?

    *random thoughts*

    This is a No Spark Code. Computer is not seeing engines revs going up after the spark is triggered, Via the crank sensor.

    And if its the only code... Back to basics. Battery connections? Grounds? Bad plug, bad wire, wrong wire, fouled plug. Hmm. How old is the battery?

    ... our lady of blessed exceleration, don't fail me now ...

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