My 2007 6.0L K3500 Dually has a misfire P300

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    My 2007 6.0L K3500 Dually has a misfire P300

    Misfire PO300 or P300

    No indication of cylinder or cause, cheap code reader not a $5K snackon scantool.

    Uses alot of fuel is the only issue probably lacking power I just haven't noticed.

    According to my figures mileage is 7.8 miles to gallon unloaded.

    Next step ?
    Last edited by PAE; 05-24-2020, 11:47 AM.

    #2
    Ls swa.... never mind. Random missfire I was corrected. Did you check the connectors on the injectors and coil packs? That is the easiest thing to do since you don't have a scan tool.
    Last edited by M92PV4U; 05-22-2020, 03:16 PM.

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      #3
      To accurately diagnose a computer controlled system you need a computer to access the data. You need a friend with a good scanner that can look up the misfire data PIDs. It will tell you which one(s) are misfiring and what fuel trims are.

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        #4
        Originally posted by M92PV4U View Post
        Ls swa.... never mind.
        It's the number 3 cylinder did you check spark? Connectors on the injector and coil pack?
        No it is not the #3 cylinder, or at least that is not what a P0300 code is. It is a "random misfire" code. see what gmcxt posted above and continue on.

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          #5
          Originally posted by xr-nut View Post

          No it is not the #3 cylinder, or at least that is not what a P0300 code is. It is a "random misfire" code. see what gmcxt posted above and continue on.
          Edited.

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            #6
            If everything is good in the ignition system a cam sensor relearn is what usually fixes that code. I've done it to at least 10-12 GM trucks over the years with good results.

            Edit: might be the crank sensor relearn..... I've been out of the car business for five years and my memory isn't what it used to be.

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              #7
              Originally posted by gmcxt View Post
              To accurately diagnose a computer controlled system you need a computer to access the data. You need a friend with a good scanner that can look up the misfire data PIDs. It will tell you which one(s) are misfiring and what fuel trims are.
              Is this tool capable of doing that? Encore Professional Diagnostic Tool.

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                #8
                Originally posted by M92PV4U View Post

                Is this tool capable of doing that? Encore Professional Diagnostic Tool.
                Is that the OTC scan tool? If so, it has live date pids and will show you which hole(s) is misfiring. The last one here was a broken spark plug. Drove this truck around on a dozen test drives, no cel or any other issues. Sell it and the next day bam.....CEL. P0300 code, Snappy scanner showed the hole and found it. Somehow the end of the plug broke off.

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                  #9
                  Originally posted by xr-nut View Post

                  Is that the OTC scan tool? If so, it has live date pids and will show you which hole(s) is misfiring. The last one here was a broken spark plug. Drove this truck around on a dozen test drives, no cel or any other issues. Sell it and the next day bam.....CEL. P0300 code, Snappy scanner showed the hole and found it. Somehow the end of the plug broke off.
                  Yes it is.

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                    #10
                    Op you are about three hours away from me but it looks like I have the correct scanner.

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                      #11

                      NSEW ?
                      City or Town ?

                      Coils have been replaced, wiring / connectors good to coil packs.

                      Truck also sat for 6 months or so before and during the fire.



                      Originally posted by M92PV4U View Post
                      Op you are about three hours away from me but it looks like I have the correct scanner.
                      Last edited by PAE; 05-22-2020, 05:19 PM.

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                        #12
                        Originally posted by PAE View Post
                        NSEW ?
                        City or Town ?

                        Coils have been replaced, wiring / connectors good to coil packs.

                        Truck also sat for 6 months or so before and during the fire.



                        .
                        Attached Files

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                          #13
                          I will be headed to LA in the next few months but I dont trust this truck enough to take it down there.

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                            #14
                            One of the possibilities I've read about if all the other possibles dont pan out is a flat cam.

                            If its that this engine is toast. And will require replacement.

                            Im too old to swap out an engjne.

                            But I would supply the beer if anyone wanted to assist.

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                              #15
                              My 5.3 had a similar problem ifrc and it had a bent valve. It might be a good idea to change the spark plugs and do a compression test.

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