Incorrect engine idling speed

Engine

1. Cylinder and cylinder head

• Incorrect valve clearance
• Damaged valve train components

2. Air filter

• Clogged air filter element

Fuel system

1. Throttle body

• Damaged or loose throttle body joint
• Improperly adjusted engine idling speed (idle adjusting screw)
• Improper throttle cable free play
• Flooded throttle body
• Faulty air induction system

Electrical system

1. Battery

• Discharged battery
• Faulty battery

2. Spark plug

• Incorrect spark plug gap
• Incorrect spark plug heat range
• Fouled spark plug
• Worn or damaged electrode
• Worn or damaged insulator
• Faulty spark plug cap

3. Ignition coil

• Broken or shorted primary or secondary coils
• Faulty spark plug lead
• Cracked or broken ignition coil

4. Ignition system

• Faulty ECU
• Faulty crankshaft position sensor
• Broken generator rotor woodruff key