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Weird Misfiring problem - B6t

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    Weird Misfiring problem - B6t

    Hey guys

    I just encountered my first hicup with my 323 gt.

    It has a wierd misfire. between 2000-4000 is feels like its bogging down and after that it feels better but i think its the boost the is covering up the misfire in the higher rpms.

    Occassionally i hear a backfire/pop under the hood for no appear reason... Thats a new one to me!

    I am going to replace the fuel filter and i have a spare set of plugs wires to throw on aswell. Any suggestions on some other things to look for. My plugs are ok and gaps properly. I am thinking that its the fuel filter.

    The misfiring and shudder happens in with or without boost. But the car idles fine.

    Thanks

    #2
    Do the basics check your tune up parts... check key way play in the crank shaft pulley...

    Comment


      #3
      backfire is usually caused by unburnt fuel in the exhaust system isnt it? if thats the case, then i would check proper spark, make sure your dizzy is functioning properly. if its under a certain rpm range, i would assume its the dizzy. check the vacuum line that runs the vacuum advance for the dizzy for any kind of cracks.
      1988 323 GTX - 16psi Daily

      Comment


        #4
        Check the advance springs in the disty too.
        12 cbr250r: daily ride
        01 saab 9-3: daily
        98 gsxr 1100: for sale
        93L: money pit/ space waster
        92GL: low and slow beater
        90?: the rust free shell
        89LX: swapping to rust free shell
        89L: for sale
        89L: parts
        87 conquest: dohc 4g64 swap underway
        76+80 vw dashers: for sale

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          #5
          I Encountered the same problem after my rebuild.
          Mine is alittle worse.
          It won't hold and rmp speed between3,000-4500 is with out a horrible breaking up sound and if I holt it for more than 5 seconds it's start backfiring...so I'll be doing a basic tune up and use my handy dandy timing light....
          Lmk what caused your to act up

          Comment


            #6
            Usually (but not written in stone)...

            - disty

            - AFM

            Comment


              #7
              Also:

              Keyway
              Boost leak
              Vacuum leak

              Replace your old couplers.
              Replace your old vacuum lines.
              Check your grounds, add a few more.

              Comment


                #8
                My money is on keyway or dizzy springs.

                1988 White GTX - #1 parts
                1988 Black GTX - #2 reliably broken touge monstar (294,000 miles no rebuilds) - dead
                1988 Blue GTX - #3 in progress (view here)
                1988 Blue GTX - #4 BPT swapped weekend warrior.
                1988 White GTX - #5 Rally car

                Comment


                  #9
                  I have a similar issue in my daily driver 91 capri XR2

                  I have slight hesitation if your steady on the gas, feels like somethings holding the car back, then it feels like it breaks free when you hit boost, really strange. Does not happen if your on the gas hard though, but as you said I think the boost is hiding the issue.

                  I am thinking it might be a small boost leak, I changed the IAC, TPS, dizzy, adjusted timing, plugs, wires, and ect. Also just did timing belt and waterpump and no issues with the keyway.

                  Hope you get it figured out, I know mine is driving me up a wall.

                  Comment


                    #10
                    Originally posted by Jackrobot View Post
                    I have a similar issue in my daily driver 91 capri XR2

                    I have slight hesitation if your steady on the gas, feels like somethings holding the car back, then it feels like it breaks free when you hit boost, really strange. Does not happen if your on the gas hard though, but as you said I think the boost is hiding the issue.

                    I am thinking it might be a small boost leak, I changed the IAC, TPS, dizzy, adjusted timing, plugs, wires, and ect. Also just did timing belt and waterpump and no issues with the keyway.

                    Hope you get it figured out, I know mine is driving me up a wall.
                    Exact problem I experienced while commuting to work. I happened to notice that my Voltage reading was a bit low, then shortly after my alternator died (replaced several times). Turned out to be a badly corroded NEGATIVE (-) battery cable. Replaced cables, replaced ground leads in engine bay, been running normally ever since.

                    Comment


                      #11
                      I'll have to try that, I replaced one engine ground but haven't had much time to mess with anything else, gonna change the alt, belts since they are cracking, and I'll do the - cable and some more grounds and see what happens. Vac lines also, and some other things.

                      Gonna swap my FMIC setup I built from my other 91 XR2 since I'm doing either a motor and turbo, or turbo and motor work upgrade on, just to make sure I don't have a boost leak hah

                      Comment


                        #12
                        Originally posted by Jackrobot View Post
                        I have a similar issue in my daily driver 91 capri XR2

                        I have slight hesitation if your steady on the gas, feels like somethings holding the car back, then it feels like it breaks free when you hit boost, really strange. Does not happen if your on the gas hard though, but as you said I think the boost is hiding the issue.

                        I am thinking it might be a small boost leak, I changed the IAC, TPS, dizzy, adjusted timing, plugs, wires, and ect. Also just did timing belt and waterpump and no issues with the keyway.

                        Hope you get it figured out, I know mine is driving me up a wall.
                        I have had a very simular problem with my GTX... I never found out the answer to it as I blew up the transmission and the car hasn't been on the road since.... here is what I found... Key way was fine, tryed 2 different dizzy's one with brand new spring set I installed from mazda.. tryed different ecu's... adjusted and played with tps... tryed different vaf sensors... new plugs, and wires..

                        AF gauge showed that my problem was caused because the car was going lean... a check of my fuel injector pulse width showed that the car was commanding the flat lean spot.. when I watched the pulse width rather then seeing a nice smooth rappid curve come on as boost came on I saw a flat spot at 7ms then a spike to 20ms....

                        If you figure it out let me know..

                        Comment


                          #13
                          Do you have a Voltmeter installed? What is it reading at idle and while cruising?

                          Comment


                            #14
                            Originally posted by BFMRGTX View Post
                            Do you have a Voltmeter installed? What is it reading at idle and while cruising?
                            no I don't.. but I never had any problems with lights dimming, starting after sitting, battery dieing, or anything related to bad grounding or poor alternator output..

                            also like I mentioned my problem is an ecu commanded problem.. there is an input problem causing the ecu to command my flat/lean spot as I found out when checking the injector pulse width...

                            one thing I know I also needed to check but never did was my coolant temp senor on the thermostat housing..

                            Comment


                              #15
                              i have some of the problems people have posted and changed the water pump a while back and redid the timing but have been wondering what to set it at. i have it at 11 degrees from tdc. well that's what it shows at the crank pulley. just wondering if this correct or should i redo it? don't mean to thread jack just had a question.

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