Engine Hesitates

Check fuel pressure.
Check ignition and valve timing.
Check spark plugs.
Check for contaminated fuel.
Check cooling system.
Check for low compression.
Check for vacuum leaks.
Check throttle position sensor (if equipped).
Check for clogged fuel filter.
Check for clogged air filter.
Check for clogged MAP sensor (pressure sensor) vacuum hose (if equipped).
Check for faulty ECM.
Check for faulty coolant (water) temperature sensor.
Check for malfunctioning electronic fuel injection system.
Check for malfunctioning EGR valve (if equipped).
Ensure sufficient secondary spark is available.