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Misfire is driving me completely bonkers, help!

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  • Question : Misfire is driving me completely bonkers, help!

    Hey guys,

    I still have a problem with misfiring. I have replaced the following with new/remanufactured

    Injectors
    Plugs
    Leads
    Cap
    Rotor arm
    Coil pack
    Fuel pump
    fuel filter
    Fuel feed line
    Fuel return line
    Fuel tank
    All vacuum pipes & lines
    Pacesetter headers
    K&N filter with custom ducting which includes stock MAF
    IAT sensor
    195 stat
    16lbs rad cap

    I have removed the following

    EGR complete system
    Air/smog pump and all associated piping
    Carbon canister and all associated pipes wiring
    Cat (replaced with straight through)

    The following are original NOT REPLACED parts

    Fuel pressure regulator
    Injectors harness
    O2 sensor
    MAF
    Coolant temp sensor

    I retimed it to 10BTDC (OEM) yesterday as it was about 5 degrees out and since then it's been misfiring like crazy. And yes I did it at operating temperature so the lack of IAT sensor readings wouldn't affect it.

    Battery has been disconnected for a good hour to clear any codes and once running it gives me no codes at all despite not having an EGR.

    Anyone got any idea why I have a random misfire? It's driving me absolutely mental. And another thing is that the temperature on the gauge never gets higher than just over 100F, despite the fan citing in and out and the area around the sensor being 89C. What's that all about?!

    Listen to this but make sure you have your bass turned up so you can hear the 'popping'....

    Last edited by 3rdgen8284; 11-27-2016, 11:29 AM.
    www.early3rdgen.com
    www.knight.industries

    1984 Firebird S/E with 2.8 V6 MPFI motor, drivetrain and loom from a 1985.
    Mods include custom cold air K&N system, Pacesetter 70-1206 Headers, de-cat, stock V8 exhaust.
    Smog delete, EGR delete.

  • #2
    Wow! What a response
    www.early3rdgen.com
    www.knight.industries

    1984 Firebird S/E with 2.8 V6 MPFI motor, drivetrain and loom from a 1985.
    Mods include custom cold air K&N system, Pacesetter 70-1206 Headers, de-cat, stock V8 exhaust.
    Smog delete, EGR delete.

    Comment


    • #3
      Originally posted by 3rdgen8284 View Post
      Wow! What a response
      This forum has been quite slow recently. I'm not at all surprised.

      This is going to sound incredibly elementary, but have you checked to see if the plug leads are going to the correct cylinders? I had #2 and #6 crossed recently, and it missed like mad. Swapped them to the correct holes, and all was well.
      Kaiser George IX: 1996 Buick Century Special wagon. 213-SFI. 250k miles. Never gonna give you up, never gonna let you down. First documented LX9 swap in an A-body! Click here to read my build thread!

      Comment


      • #4
        Surely it would miss cold or warm though?
        www.early3rdgen.com
        www.knight.industries

        1984 Firebird S/E with 2.8 V6 MPFI motor, drivetrain and loom from a 1985.
        Mods include custom cold air K&N system, Pacesetter 70-1206 Headers, de-cat, stock V8 exhaust.
        Smog delete, EGR delete.

        Comment


        • #5
          The fan is turning on and off? Coolant temp sensor would do that. Had that go bad on me along with a major problem caused by aftermarket coils(Accel). Be warned, there are two firing orders running around on the web. One is right and the other wrong. List what you have and we can go from there.
          My misfires seemed to come and go. One day it's just fine the next it was running like crap.
          95 Beretta 3100 with 3400 intakes and TCE TB
          High flow cat and a Magnaflow muffler
          Grand Prix trans with 3.33FDR

          Comment


          • #6
            Yes cooling fan is cutting in and out. The 2.8 MPFI has three coolant sensors though doesn't it? Ok i'm working on this firing order;

            WINDSHIELD

            5 6
            3 4
            1 2

            COOLING FAN

            This runs fine when cold, and misses like hell when its warm.
            www.early3rdgen.com
            www.knight.industries

            1984 Firebird S/E with 2.8 V6 MPFI motor, drivetrain and loom from a 1985.
            Mods include custom cold air K&N system, Pacesetter 70-1206 Headers, de-cat, stock V8 exhaust.
            Smog delete, EGR delete.

            Comment


            • #7
              It would be near the water neck. Didn't read you name and was thinking that you had a FWD. There are changes between the FWD and RWD 2.8/3.1's that I don't know about.
              95 Beretta 3100 with 3400 intakes and TCE TB
              High flow cat and a Magnaflow muffler
              Grand Prix trans with 3.33FDR

              Comment


              • #8
                Did you get a new coolant temperature sensor yet?
                95 Beretta 3100 with 3400 intakes and TCE TB
                High flow cat and a Magnaflow muffler
                Grand Prix trans with 3.33FDR

                Comment


                • #9
                  Sorry for delay, for some reason this forum doesn't send me an email when someone posts on the threads!

                  I wasn't convinced the info I'd been given about the cylinder numbers was correct. It wasn't! I'd set No. 2 up as No.1. So I dismantled the lot and re-connected the wires and re-timed it again! It ran MUCH better but I'm still getting a temp variation between the front and the back of the motor.

                  The rear sensor is at about 102C and the front sensors are reading 80C, so I'm pretty sure the rear emergency fan override sensor is the one triggering the fan. Also the motor is idling at 1100RPM instead of 800 so I'm wondering hat is causing that. There are no vacuum leaks so I'm a bit lost with it but it's driving me nuts!
                  www.early3rdgen.com
                  www.knight.industries

                  1984 Firebird S/E with 2.8 V6 MPFI motor, drivetrain and loom from a 1985.
                  Mods include custom cold air K&N system, Pacesetter 70-1206 Headers, de-cat, stock V8 exhaust.
                  Smog delete, EGR delete.

                  Comment

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