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wayne 10/24/2012
1984 Nissan 720 Deluxe 4 Cyl 2.5L - Engine
engine hesitates when trying to accelerate, almost like it wants to cut out
replaced egr valve and replaced several vacuum lines. noticed AB valve has seepage around seam and thermo vacuum valve and VVT look like original equipt. 241,000 on eng runs great when getting past hesitation
1 Answer
  • Jimm
    Jimm 10/31/2012
    First step - have the check engine light scanned - for free - at any local auto parts store; Advance Auto, Auto Zone, NAPA. Then, post a reply as 'add answer' for more assistance.

    Possible Causes of Engine Hesitation or Stumble:

    Dirty fuel injectors (cleaning the injectors often fixes this)
    Dirty air filter (change filter)
    Dirty / clogged fuel filter (change filter)
    Bad MAP (manifold absolute pressure) sensor
    Bad TPS (throttle position) sensor
    Bad or dirty MAF (mass airflow) sensor
    Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
    Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
    Bad gasoline (fuel contaminated with water or too much alcohol)

    Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

    Dirty or worn spark plugs
    Bad plug wires
    Weak ignition coil
    Wet plug wires

    wayne 11/3/2012
    accelerator pump was leaking, replaced problem still there had to order fuel filter

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