help with dtc p0300

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  • bullpup12
    Junior Member
    • Jan 2013
    • 1

    help with dtc p0300

    1st time here. I have a 02 blazer 4.3 with dtc p0300 random misfire. Engine seems to run great, have changed cayt, plugs,cap,rotor, injectors, cam sensor, crank sensor,distributor, and have even changed complete engine with still the same dtc showing back. 0 misfires at idle, but very many with acceleration mainly only on cyl 1 and 4. ANY HELP?
  • David Green
    Senior Member
    • Oct 2009
    • 382

    #2
    Originally posted by bullpup12
    1st time here. I have a 02 blazer 4.3 with dtc p0300 random misfire. Engine seems to run great, have changed cayt, plugs,cap,rotor, injectors, cam sensor, crank sensor,distributor, and have even changed complete engine with still the same dtc showing back. 0 misfires at idle, but very many with acceleration mainly only on cyl 1 and 4. ANY HELP?
    I'd recommend you book yourself on some Snap On diagnostic training courses either through their website or your local snap on dealer.

    Comment

    • Joe Rappa
      Snap-on DSD
      • Aug 2007
      • 2050

      #3
      When it says it is misfiring, does it feel like it is missing?

      Joe
      "You don't build a reputation on what you're going to do"
      Henry Ford

      Comment

      • Witsend
        Banned
        • Nov 2012
        • 2942

        #4
        but very many with acceleration mainly only on cyl 1 and 4. ANY HELP?
        Reply With Quote
        mist the spark plug wires and coil with a spray bottle with water. Watch and listen for spark arcing in a darker area , especially around the coil tower.
        If you dont see it clip a jumper wire to a good ground and run the other end along the coil tower coil wire and #1 And #4 cable to see if you have spark leakage.

        Comment

        • hhong12dlm
          Junior Member
          • Mar 2013
          • 22

          #5
          Originally posted by bullpup12
          1st time here. I have a 02 blazer 4.3 with dtc p0300 random misfire. Engine seems to run great, have changed cayt, plugs,cap,rotor, injectors, cam sensor, crank sensor,distributor, and have even changed complete engine with still the same dtc showing back. 0 misfires at idle, but very many with acceleration mainly only on cyl 1 and 4. ANY HELP?
          a few things that Ive had cause odd misfire problems on that engine
          bad aftermarket dist cap, use oe delco cap and rotor, see if 1 and 4 run near each other in cap, check the rotor free play back and forth if excessive it can cause miss. pull the crank sensor and inspect to see if it has any rub marks, may need cover or shim.

          Comment

          • Solees
            Junior Member
            • Oct 2014
            • 7

            #6
            Have you looked at the freeze frame data, is there any indication of a lean condition from the fuel trims? Does the check engine light blink when the misfire occurs? Possibly a fuel pump or filter problem.

            Comment

            • maven
              Senior Member
              • Mar 2014
              • 269

              #7
              Well with everything you have replaced so far simple process of elimination would lead one to closely inspect the wiring before condemning the PCM. The fact that engine replacement and most of the other replacements had no affect seem to dictate that some potentially obvious electrically was missed.

              Comment

              • Melbar
                Junior Member
                • Jan 2011
                • 3

                #8
                You guys realize, this thread is over two years old, right?

                Comment

                • Witsend
                  Banned
                  • Nov 2012
                  • 2942

                  #9
                  You guys realize, this thread is over two years old, right?
                  Bwahhaaaa, never say die for if you have faith the size of a mustard seed that falls on fertile manured ground, in a couple years or so it can sprout new roots and grow into a great tree someday that can derail everyone's train of thought

                  Comment

                  • sbreland73
                    Senior Member
                    • Jan 2009
                    • 1076

                    #10
                    Originally posted by Melbar
                    You guys realize, this thread is over two years old, right?
                    My thoughts also. One would hope this case has been fixed by now.
                    S. Breland

                    Comment

                    • chaskuss
                      Senior Member
                      • Dec 2009
                      • 192

                      #11
                      Originally posted by sbreland73
                      My thoughts also. One would hope this case has been fixed by now.
                      Fixed or not, for future members checking out this thread, it's best if someone actually answers the question. The thread is worthless, if no one answers the original question.

                      Charlie

                      Comment

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