Engine won't start
- Loose or corroded battery connections
- Discharged or defective battery
- Faulty, loose or open wiring in the starter circuit
- Faulty traction relay or starter switch
- Faulty starter
- Electric starter gear or flywheel teeth loose or broken
- Motor ground damaged or disconnected
Engine turns over but won't start
- Fuel tank empty
- Battery low (motor rotates slowly)
- Loose or corroded battery connections
- Wet or Damaged Ignition System Components - Gasoline Engine Models
- Faulty, loose or open wiring in the ignition circuit - gasoline models
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Faulty Preheating System - Diesel Models
- Throttle Mechanism Improperly Adjusted, Worn, or Sticking - Carburetor Gasoline Models
- Defective Fuel Cutoff Valve Coil - Gasoline Carburetor Models
- Damage to the Fuel Injection System - Fuel Injected Petrol Models
- Faulty fuel cut-off valve - diesel models
- Air in the Fuel System - Diesel Models
- Major mechanical failure (e.g. camshaft drive)
Engine difficult to start from cold
- Battery low
- Loose or corroded battery connections
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Faulty Preheating System - Diesel Models
- Throttle Mechanism Improperly Adjusted, Worn, or Sticking - Carburetor Gasoline Models
- Damage to the Fuel Injection System - Fuel Injected Petrol Models
- Other Ignition System Damage - Gasoline Models
- Fast idle valve incorrectly adjusted - diesel models
- Low compression in the engine cylinders
The engine is difficult to start when it is hot
- Air filter element dirty or clogged
- Throttle Mechanism Improperly Adjusted, Worn, or Sticking - Carburetor Gasoline Models
- Damage to the Fuel Injection System - Fuel Injected Petrol Models
- Low compression in the engine cylinders
Starter makes noise
- Electric starter gear or flywheel teeth loose or broken
- Starter mounting bolts are loose or missing
- Internal starter components worn or damaged
Engine starts but immediately stalls
- Ignition Circuit Connectors Loose or Faulty - Gasoline Models
- Vacuum leak in carb/throttle body or intake manifold - petrol models
- Clogged jets or internal carburetor passages - gasoline models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
Unstable operation in idle mode
- Clogged air filter element
- Vacuum leak in carb/throttle body, intake manifold or related hoses - petrol models
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Unequal or low compression in the engine cylinders
- Worn camshaft cams
- Drive chain installed incorrectly
- Clogged jets or internal carburetor passages - gasoline models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
- Faulty Injector - Diesel Models
Misfire at idle speed
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Spark Plug High Voltage Wiring Faulty - Gasoline Models
- Vacuum leak in carb/throttle body, intake manifold or related hoses - petrol models
- Clogged jets or internal carburetor passages - petrol models with carburetor
- Injector Clogged/Fuel Injection System Damaged - Fuel Injected Petrol Models
- Injector Defective - Diesel Models
- Distributor breaker cover split - petrol models (where applicable)
- Unequal or low compression in the engine cylinders
- Disconnected or damaged crankcase ventilation hoses
Misfiring throughout the entire speed range
- Clogged fuel filter
- Fuel pump defective or supply pressure low
- Clogged fuel tank opening or fuel lines
- Vacuum leak in carb/throttle body, intake manifold or related hoses - petrol models
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Spark Plug High Voltage Wiring Faulty - Gasoline Models
- Faulty Injector - Diesel Models
- Distributor breaker cover split - petrol models (where applicable)
- Faulty ignition coil - petrol models
- Unequal or low compression in the engine cylinders
- Clogged jets or internal carburetor passages - petrol models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
Engine accelerates with a delay
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Vacuum leak in carb/throttle body, intake manifold or related hoses - petrol models
- Clogged jets or internal carburetor passages - gasoline models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
- Faulty Injector - Diesel Models
Engine stalls
- Vacuum leak in carb/throttle body, intake manifold or related hoses - petrol models
- Clogged fuel filter
- Fuel pump defective or supply pressure low
- Clogged fuel tank opening or fuel lines
- Clogged jets or internal carburetor passages - gasoline models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
- Faulty Injector - Diesel Models
Insufficient engine power
- Drive chain installed incorrectly
- Clogged fuel filter
- Fuel pump defective or supply pressure low
- Unequal or low compression in the engine cylinders
- Worn, defective, or improperly gapped spark plugs - Gasoline Models
- Vacuum leak in carb/throttle body, intake manifold or related hoses - petrol models
- Clogged jets or internal carburetor passages - gasoline models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
- Faulty Injector - Diesel Models
- Improper Injection Timing - Diesel Models
- Wheel braking
- Clutch slip
The oil pressure warning light comes on when the engine is running
- Low oil level or wrong type of oil filled
- Faulty oil pressure sensor
- Worn engine bearings and/or oil pump
- High engine operating temperature
- Defective oil pressure relief valve
- Clogged oil pump intake strainer
Engine continues to run after shutdown
- Excessive soot in the engine
- High engine operating temperature
- Defective Fuel Cutoff Valve Coil - Gasoline Carburetor Models
- Damage to the Fuel Injection System - Fuel Injected Petrol Models
- Faulty fuel cut-off valve - diesel models
Noises in the engine
Detonation or knocking during acceleration or when the vehicle is loaded
- Incorrect Ignition Timing/Ignition System Damage - Petrol Models
- Wrong Brand Spark Plugs Installed—Gasoline Models
- Filled with the wrong type of fuel
- Vacuum leak in carb/throttle body, intake manifold or associated hoses - petrol models
- Excessive soot in the engine
- Clogged jets or internal carburetor passages - gasoline models with carburetor
- Clogged Injector/Fuel Injection System Damaged—Fuel Injected Petrol Models
Whistling or wheezing noises
- Leaking intake manifold or carburetor/throttle body gasket - petrol models
- Leaking exhaust manifold gasket or tube-to-manifold connection
- Vacuum hose lets air through
- Blown cylinder head gasket
Light tapping or rattling
- Worn valve train or camshaft
- Auxiliary components damaged (water pump, generator, etc.)
Loud or dull thud
- Worn connecting rod bearings (regular loud knocking, possibly decreasing when the car is loaded)
- Worn main bearings (loud knocking, possibly worse when the car is loaded)
- Piston damaged (most noticeable when the engine is cold)
- Auxiliary components damaged (water pump, generator, etc.)
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