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Losing throttle response at 2000 rpm

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  • #1

    Losing throttle response at 2000 rpm

    1. I have a XT model intake and finally am able to start tuning this thing in. I am finding that when first starting it up and taking off the throttle is jerky but will level out after a few minutes. However, when cruising or taking off from a light you step on the gas (it moves) but its like there is no response until you keep pushing it down and the car jerks to life. I tried to monitor the EFI tablet when it does this. What I am finding is when you take pressure off the throttle the AFR goes from 13.4 to 23-24 (lights up red) until it snaps back to life and goes back down to 13.4. Any idea what could be causing this?? I wanted to let the car self learn without messing with it but i have to feather the clutch and don't want to burn it up.

    2. Also, is the manifold vacuum supposed to be in the negatives?? It isn't in the red zone but I wasn't sure what the range is supposed to be.

    Thanks in advance!
    Tags: None
  • #2
    What is the water temperature at when you try to drive it?
    In my neighborhood, if you open your hood to check your oil, and the vehicle still runs after you close it.......Then your labeled the Neighborhood Mechanic.

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    • #3
      Water temp is at 185-200 depending on conditions. It seems like it does it much more once it’s up to temperature

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      • #4
        Do you have the air temperature sensor installed, and connected?
        Have you gone through the "Acceleration Fuel" page and made adjustments?
        In my neighborhood, if you open your hood to check your oil, and the vehicle still runs after you close it.......Then your labeled the Neighborhood Mechanic.

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        • #5
          Air temp sensor is installed. The acceleration page, no. I completed the setup wizard and let it learn from there.

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          • #6
            Go to the acceleration page and touch the ? at the top of the page. It will show you how to use the settings.
            In my neighborhood, if you open your hood to check your oil, and the vehicle still runs after you close it.......Then your labeled the Neighborhood Mechanic.

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            • #7
              I played with this today... I tried to adjust the the throttle in the three areas but all it managed to do was cause the car to stall out when you let off the throttle (was not doing that before). I did notice that when the AFR shoots up randomly around 2000RPM both "loops" go from green to red before the car comes back to life. I was reading the forums and seen somewhere it was not suggested to run E3 plugs because they will interfere with the CPU; is this true? Could this be the issue?

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              • #8
                Change out the spark plugs immediately to regular plugs.

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                • #9
                  Originally posted by goodolboy0404 View Post
                  I played with this today... I tried to adjust the the throttle in the three areas but all it managed to do was cause the car to stall out when you let off the throttle (was not doing that before). I did notice that when the AFR shoots up randomly around 2000RPM both "loops" go from green to red before the car comes back to life. I was reading the forums and seen somewhere it was not suggested to run E3 plugs because they will interfere with the CPU; is this true? Could this be the issue?

                  Good ole boy,

                  Check that you did not mistakenly swap the TPS & Fuel P wires.....They will plug in.

                  TPS is located on the side of throttle body.
                  Fuel P plugs into sensor on inlet of fuelrail.

                  Note: Do not use E3 plugs, they dont play well with PF4.
                  Last edited by 2700 Cast; 08-10-2020, 12:28 PM.

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                  • #10
                    You need resistor plugs of the correct reach and thread pitch. Non-resistor plugs will cause issues with timing controlled EFI. I know nothing about E3 plugs. I use cheap Autolite plugs. Never a problem.

                    Played with all three areas in the Acceleration Fuel function is not the best idea unless you are familiar with exactly what they do. If you lowered the Decel Fuel Cut RPM threshold too far, your motor could stall getting off the throttle. My motor responds better to an increase in the Decel Fuel Cut RPM threshold.

                    You can get good results working with the Fuel Modifiers function. As far as I can tell, that function customizes the fuel map if Self Learn is not giving you satisfactory results. Read the help several times and make note of how the load zones work and where you are having issues with the overall performance in those load zones. Then make small changes as advised in the instructions. Really can help a lot, but takes some patience. Also helps a lot if you know the difference in how a motor runs and sounds when slightly lean or slightly rich. Unfortunately, that can't be taught in a message box.

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                    • #11
                      I am going to swap out the plugs and I found the vacuum line from the intake to the fuel pressure regulator was off. I’m assuming that’ll cause issues too?

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                      • #12
                        A little. It depends on your elevation.
                        In my neighborhood, if you open your hood to check your oil, and the vehicle still runs after you close it.......Then your labeled the Neighborhood Mechanic.

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                        • #13
                          C9C90B1E-7C0B-4BEC-AE81-1946A879BB23.jpegSo, replaced the E3 with Autolite 605’s and gapped them. Ran a vacuum line from the designated port on the intake to the fuel pressure regulator, found the fuel pressure was about 9 lbs off at idle (with the hose disconnected). So i readjusted that. Still having the throttle stall on me. I turned on diagnostic mode to see if that’d tell me anything.... when the throttle stops responding the throttle sensor goes from green to red and then the O2 sensor does the same. Slowly apply the throttle, the sensor goes green and the O2 sensor follows. No other sensors are turning red.... could this be the issue? A bad O2 sensor or throttle sensor?
                          Last edited by goodolboy0404; 08-11-2020, 11:19 PM.

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                          • #14
                            A screenshot of the " Digital Display " would show more info.

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                            • #15
                              I guess I’m asking if the throttle and O2 sensor are supposed to all of sudden stop working and turn red (like they are off).

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