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Engine stumbling/bogging when bangshifting manual trans

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  • Engine stumbling/bogging when bangshifting manual trans

    What should I look for when my engine "shuts down" like a second or so when I'm doing WOT acceleration and shifting gears very fast? Tried to adjust accelerator pump settings on my phone but no improvement so far, missing second and a half of my ET vs. carb last year and 8 mph trap speed.. Seems like proflo can't keep up with fast ON-OFF-ON throttle movements when shifting? After you hit gaspedal again after lifting for shifting there is delay after engine wakes up and starts pulling again. Trying to get it on video later this week when weather gets better. Any other having this problem with manual transmissions?

  • #2
    how long have you let the system learn ? take a video of the problem and post hear for the mod's they will help.

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    • #3
      Try bringing the Decel Fuel Cut up to 1500.

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      • #4
        No problem here, but yes raise your Decel fuel Cut-Off.
        70 Dodge Charger R/T 540 Pro-Flo 4 Fed
        70 Dodge Coronet Wagon 360 soon to be Pro-Flo 4 fed.

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        • #5
          It has been learning about 1000 miles now, I don't remember this problem being so apparent earlier this year before I had to hassle with ECU and reset self-learn and load basemap again. I think my Decel fuel cut off was initially 1500 and have been trying to pump it up to 6000 and have also adjusted pump shot up to 50% so far.

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          • #6
            I have experienced this also.
            69 L78 396
            It happens so infrequently that it was difficult to determine the cause .
            I caught it on a screen shot twice. The fuel pressure drops to basically 0 for about 1 sec under hard acceleration when you shift.
            It comes back immediately.
            I do not know the cause.
            I haven’t noticed it recently. I need new rear tires.
            I’m running the Edelbrock sump system.

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            • #7
              Ok, went on a test drive..Here is some videos of recording my android screen: (Let me know if videos don't open, I set them to open only for people using links below)

              1-2 shift not responsing to throttle until I lift a little and hit it again:



              1st pull on this video, 1-2 shift ok, 2-3 hesitating like on first video. 2nd pull on this video 1-2 ok, 2-3 engine died, I kept throttle at 100% to see if it wakes up if I keep on it longer, it didn't. Tried starting while rolling, not starting. Stopped and waited a little and then it started again:



              On this video clean shifts all the way to 3rd gear:



              Little gear miss on 1-2 shift but otherwise ok:



              On the way back home I made light acceleration on gravel road on 4th gear, maybe TPS% up to 50% and engine died again. Had to stop and wait for main relay click off and then it primed fuel pump and started right away. I noticed when I watched my screen recordings, seems like fuel pressure is all over the place when moving throttle from 100 to 0 back to 100..I'm running Edelbrock fuel sump system powered thru EFI harness, no external relay.

              I also made adjustments prior this test drive and adjusted pump shot to +99%, pump shot time maxed out at 5, and decel fuel cut off was I think 3000rpm. Weird how I first tried to adjust pump shot to +100% and hit "Finished" and went back to see if it saved, it was showing -100%. Did it twice, then I lowered it down to +99% and then it saved correct value.

              This adjustments helped a little, now it only stumbles like 50/50 of time, but last saturday on test'n'tune day on a strip it was doing this on every pass I made, so didn't get anything positive out of that day, except new 60ft record..

              Comment


              • #8
                Originally posted by 1969L78 View Post
                I have experienced this also.
                69 L78 396
                It happens so infrequently that it was difficult to determine the cause .
                I caught it on a screen shot twice. The fuel pressure drops to basically 0 for about 1 sec under hard acceleration when you shift.
                It comes back immediately.
                I do not know the cause.
                I haven’t noticed it recently. I need new rear tires.
                I’m running the Edelbrock sump system.
                Thanks for letting me know, got in on video too today^^

                Comment


                • #9
                  This just came to my mind, I have Fuel pump PWM ON, could this be the problem, should fuel pump run 100% speed all the time no matter the TPS% if I set PWM control OFF???

                  I also have vacuum line attached to fuel sump pump system, and I noticed that my vacuum goes momentarily around 25in.hg when shifting, could it cause the fuel pressure to drop so hard?

                  Last edited by BBDart; 09-23-2020, 10:52 AM.

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                  • #10
                    from the e-tuner manual page 7.
                    Fuel Sump PWM: This option should be ON if using the Edelbrock Fuel Sump and OFF
                    for all other fuel systems

                    there has a been a lot of complaints with the sump fuel system . all who have switched to in tank are happy.

                    Comment


                    • #11
                      Originally posted by BBDart View Post
                      Ok, went on a test drive..Here is some videos of recording my android screen: (Let me know if videos don't open, I set them to open only for people using links below)

                      1-2 shift not responsing to throttle until I lift a little and hit it again:



                      1st pull on this video, 1-2 shift ok, 2-3 hesitating like on first video. 2nd pull on this video 1-2 ok, 2-3 engine died, I kept throttle at 100% to see if it wakes up if I keep on it longer, it didn't. Tried starting while rolling, not starting. Stopped and waited a little and then it started again:



                      On this video clean shifts all the way to 3rd gear:



                      Little gear miss on 1-2 shift but otherwise ok:



                      On the way back home I made light acceleration on gravel road on 4th gear, maybe TPS% up to 50% and engine died again. Had to stop and wait for main relay click off and then it primed fuel pump and started right away. I noticed when I watched my screen recordings, seems like fuel pressure is all over the place when moving throttle from 100 to 0 back to 100..I'm running Edelbrock fuel sump system powered thru EFI harness, no external relay.

                      I also made adjustments prior this test drive and adjusted pump shot to +99%, pump shot time maxed out at 5, and decel fuel cut off was I think 3000rpm. Weird how I first tried to adjust pump shot to +100% and hit "Finished" and went back to see if it saved, it was showing -100%. Did it twice, then I lowered it down to +99% and then it saved correct value.

                      This adjustments helped a little, now it only stumbles like 50/50 of time, but last saturday on test'n'tune day on a strip it was doing this on every pass I made, so didn't get anything positive out of that day, except new 60ft record..
                      [email protected] Email your contact phone number

                      Don't get too caught up in the numbers.
                      Just give the Engine what it wants &
                      Let the numbers be what they are.

                      Jim McFarland....

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                      • #12
                        where else do you get service like this from any where 2700 cast is my hero

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                        • #13
                          I think I got this fixed for now. Removed vacuum reference from fuel sump and added some pump shot % and it works as it should. Also had to re-adjust my fuel pressure to 58psi, it was reading 54psi even though I adjusted it to 58psi at spring this year. When I look back to my carburetor times, I remember my 440 needed the most aggressive accelerator pump cam you can install on 35cc pumps on Holley DP carb so I think my pump shot adjustments are justified..

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                          • #14
                            What would cause the vacuum reference system to induce this kind behavior in the fuel sump pressure regulator ?

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                            • #15
                              Yeah,
                              something is amiss here. You should not have to remove vacuum source.

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