Erratic Idle (Warm-Up)

Check throttle position switch and connection.
Check coolant temperature sensor and connection.
Check idle actuator and idle (air) control valve.
Check Motronic Control Unit (MCU).
Check air temperature sensor and airflow sensor.
Check coolant temperature sensor.
Ensure spark plugs fire.
Check ignition and sensor wires for proper connection.
Check distributor.
Check ignition and coil circuit.
Check intake system.
Check coolant.