Intermittent Bucking & Jerking

Check ignition system secondary wires, distributor cap and rotor, Thick Film Integrated (TFI) ignition module, engine spark, plug firing voltages, cylinder balance, and base ignition timing. Check spark plugs for fouling and proper gap.
Perform QUICK TEST . Connect Manifold Absolute Pressure (MAP)/Barometric Pressure (BP) tester to MAP or BP sensor (depending on vehicle). Check readings with engine off and with ignition switch in "ON" position. Compare reading with MAP/BP SPECIFICATIONS table.
On Vane Airflow Meter (VAF) equipped vehicles, check for unmetered air leaks. Check for loose air tubes, missing hoses, or vacuum plugs.