98 F-150 4.6 misfire no cell!

Discussion in 'Engine & Performance' started by Mamba2485, Jul 11, 2019.

  1. Mamba2485

    Mamba2485 Junior Member

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    I have a 1998 F-150 4.6 191000 miles ,I have replaced coil packs,wires, injectors, throttle body,mass air flow,plugs still missing out on idle and under load but you can hold throttle at 1500 rpm you can hear miss and feel it,it will try to smooth out then goes back to missing and fuel pressure 30 to 40 psi any help would be appreciated!
     
  2. Roush PSD Interceptor

    Roush PSD Interceptor Straight Piped Diesel Staff Member

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    @Mamba2485

    Recommended fuel pressure is 55-85lbs

    When was the last time you changed the fuel filter ?

    Could be the fuel pump driver module or the
    fuel pump it self.
    That is an expensive pump module.
    Since you have fuel pressure I wouldn't think it's the module.
    The fuel pump could be getting weak if the filter has been
    changed very recently.
     
  3. Roush PSD Interceptor

    Roush PSD Interceptor Straight Piped Diesel Staff Member

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    If you go through everything fuel wise, ie filter change first.
    Check the tank expansion vent line.
    Mud daubers, and dirt bees can plug this line causing the fuel tank
    to not vent and draw suction on it making the fuel pump work harder
    over time.

    Usually the symptoms are if this is the cause, runs great for a while,
    then gets worse and worse.
     
  4. Roush PSD Interceptor

    Roush PSD Interceptor Straight Piped Diesel Staff Member

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    Give us an update on what you find.
     

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