Engine
1. Cylinder(s) and cylinder head(s)
- Incorrect valve clearance
- Damaged valve train components
2. Air filter
- Clogged air filter element
Fuel system
1. Throttle body (-ies)
- Damaged or loose throttle body joint
- Improperly synchronized throttle bodies
- 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(s)
- Incorrect spark plug gap
- Incorrect spark plug heat range
- Fouled spark plug
- Worn or damaged electrode
- Worn or damaged insulator
3. Ignition coil(s)
- Broken or shorted primary or secondary coils
- Cracked or broken ignition coil
4. Ignition system
- Faulty ECU
- Faulty crankshaft position sensor