The engine does not start
- The battery is discharged
- Loose battery connections
- The ignition wiring is loose or broken
- Moisture on spark plugs, distributor cap, or high tension wires
- Incorrect spark plug
- The distributor cap or runner is cracked
- Dirt or water in the carburetor
- Empty fuel tank
- Defective fuel pump
- Defective starter
- Low compression in engine cylinders
The engine stalls
- Incorrect idle speed adjustment
- Air leak from intake manifold
- Incorrect ignition timing
Unstable idle mode
- Air leak from intake manifold
- Cylinder head gasket leak
- The camshaft lobes are worn out
- Defective fuel pump
- Loose crankcase ventilation hoses
- Incorrect idle speed adjustment
- Uneven compression in engine cylinders
Misfires
- Incorrect spark plug gap
- Ignition coil or ignition components are faulty
- Dirt or water in the carburetor
- Burnt valve
- Cylinder head gasket leak
- The distributor cover is cracked
- Uneven compression in engine cylinders
- Incorrect idle speed adjustment
Backfires
- Incorrect idle speed adjustment
- Incorrect ignition timing
- Air leak from intake manifold
- Valve stuck
Excessive oil consumption
- Worn pistons and cylinder bores
- Worn valve guides and valve stem seals
- Oil leaks through crankshaft seals, valve cover gaskets, etc.
Insufficient engine power
- Incorrect ignition timing
- Incorrect spark plug gap
- Low compression in engine cylinders
- Excessive carbon deposits in the engine
- The air filter is clogged