Rough Or Unstable Idle

Check for play in throttle cable.
Check for contaminated fuel.
Check fuel pressure.
Check EVAP control system.
Check for clogged air filter.
Check for vacuum leaks.
Check cooling system condition.
Check compression.
Check spark plugs.
Check for leaking or loose spark plug wires.
Check for adequate spark with a spark tester.
Check idle speed.
Check for cracked or burned distributor cap.
Check for worn distributor terminals.
Check ignition and valve timing.
Clogged MAP sensor vacuum hose.
Check for faulty PCM.
Check Power Steering Pressure (PSP) switch circuit.
Check for faulty Engine Coolant Temperature (ECT) sensor.
Check for faulty Intake Air Temperature (IAT) sensor.
Check for faulty A/C vacuum switching valve (if equipped).
Check for faulty Idle Air Control (IAC) solenoid valve.
Check for faulty throttle opener system (if equipped).
Check for malfunctioning EGR valve.
Check for malfunctioning PCV valve.
Check for malfunctioning electronic fuel injection system.