Rough Idle/Missing

Check for vacuum leaks (oil filler cap, oil dipstick, hose connections, PCV valve and hose).
Check air filter.
Check idle speed and ensure ignition timing is correct.
Verify secondary ignition system performance.
Verify proper compression and valve clearance.
Check variable induction system (if equipped).
Check cold start injector and cold start injector time switch.
Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
Check fuel injectors.
Check power to ECU via fusible links, fuses and EFI main relay.
Check airflow meter, coolant temperature sensor and air temperature sensor.
Check injection signal circuit.
Check O2 sensor(s).