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  • Code P0300

    I just finished my OBDII swap this week and my car is throwing code P0300 which just says Random/Multiple Cylinder Misfire. I keep on getting that code. It will go away sometimes and then come back and run like crap.

    I read on this site that had GM codes listed on it that if you find a random misfire code (P0300), the problem probably is not the ignition system. It's likely a lean fuel mixture caused by a vacuum leak or dirty injectors.

    I am already positive that it's not a dirty injector because the injectors in the car I got from Witch Hunter Performance. I am almost positive there are no vacuum leaks too. Could this code lead back to FPR, Fuel Pump or Fuel Filter?

  • #2
    I get that code when I run in boost and the hoses pop off. Oh yeah its alot of fun. After the hose pops off teh car dies, so if I give it gas at a red light, I just pray that no body hits me. But seems like a MAF code.

    Mark


    WWW.OverKillEngineeringMotorsports.com

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    • #3
      Originally posted by d.o.h.c View Post
      I get that code when I run in boost and the hoses pop off. Oh yeah its alot of fun. After the hose pops off teh car dies, so if I give it gas at a red light, I just pray that no body hits me. But seems like a MAF code.

      Mark
      I am almost positive I don't have a vacuum leak. Does the EVAP sensor on the driver side under the cover supposed to have one line open?

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      • #4
        Well what do you know, I know get a code p300. I replaced the lower and upped intake manifold gaskets and it still runs like crap. If I take it for a drive it will sometime cut out. i know my injectors are not leaking and I am almost positive I dont have a vacuum leak, although my gauge is reading low like 16.


        WWW.OverKillEngineeringMotorsports.com

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        • #5
          16 to 18 vacuum is fine. I would look into replacing the coils and ignition module if there's 8+ years old. Also make sure your fuel system is functioning properly and your other ignition system parts are in good working order.

          Are you (OP) using the 1996 fpr? I forget if you swapped that or not.
          Lifting my front wheels, one jack at a time.

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          • #6
            When I did the turbo swap I did all new everything. Every sensor has been replaced. The ICM, COILs and Wires, plugs all new. When I turn my pump on, i get 42 psi, when it stops priming it shoots down to 0 in about 10 seconds. I think I have a bad pump.


            WWW.OverKillEngineeringMotorsports.com

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            • #7
              I am using the 94 FPR, does it matter what one I used??


              WWW.OverKillEngineeringMotorsports.com

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              • #8
                Originally posted by d.o.h.c View Post
                I have a bad pump.
                There's your answer. lol I think you're missing a check ball.
                Lifting my front wheels, one jack at a time.

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                • #9
                  Not sure I am following you on this. Please explain.


                  WWW.OverKillEngineeringMotorsports.com

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                  • #10
                    Your pump should hold its prime once the key is turned off. By having it drain back so quick means that you might not be getting the right amounts of fuel when under wot under heavy load (boost) . Where did you buy the pump, and what pump is it? I wouldn't mess around any longer with taht pump you have in there. Go by a new walbro.
                    Lifting my front wheels, one jack at a time.

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                    • #11
                      I ran the PSI test agin. I get 40 when priming and 34-36 it flucuates when idleing. It is a brand new walbro, but I have ran it dry twice.


                      WWW.OverKillEngineeringMotorsports.com

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                      • #12
                        Either you have a leak somewhere or your pump is bad.
                        Lifting my front wheels, one jack at a time.

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                        • #13
                          no leaks, I checked the injectors, they are brand new as well.


                          WWW.OverKillEngineeringMotorsports.com

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                          • #14
                            So pump it is I guess.


                            WWW.OverKillEngineeringMotorsports.com

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                            • #15
                              Sounds like 88GTU is right. Bad fuel pump. Alot of pumps only need to be run dry ONCE to toast them. Get a replacement and try not to go below a 1/4 tank for at least the first month. GL.

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