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wayne 10/24/2012

1984 Nissan 720 Deluxe 4 Cyl 2.5L


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 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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