Rough/Unstable Idle

Use sound amplification tool to verify operational noise coming from fuel injector(s).
Ensure fuel system pressure is correct.
Check PCV system for restrictions.
Check coolant thermosensor for correct resistance.
Check air valve or ISC valve for malfunction.
Check connections at airflow meter or throttle body.
Check for cracks or poor connections at airflow meter or throttle body.
Check O2 sensor for 0-1.0 volt output while changing engine RPM up and down.
Verify throttle position sensor has correct adjustment and resistance value.
Check for purge valve malfunction.
Check for poor connections at airflow meter or throttle body.