Rough Idle/Missing

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