Main engine faults (Peugeot 406)

When starting the engine, the crankshaft does not rotate

• the battery terminals are not securely connected or are oxidized;
• the battery is discharged or faulty;
• damage to the wiring in the starter circuit;
• the starter traction relay is faulty;
• starter is faulty;
• the starter drive gear teeth or flywheel ring gear teeth are worn out;
• the ground bus from the engine to the vehicle body is disconnected.

The crankshaft rotates, but the engine does not start

• no fuel in tank;
• battery is low (the crankshaft rotates very slowly);
• the battery terminal is loose or oxidized;
• ignition system components are damaged (gasoline engines);
• incorrect spark plug gap (gasoline engines);
• the pre-heating system is faulty (diesel engines);
• fuel injection system damage (gasoline engines);
• the electromagnetic valve that shuts off the fuel supply is faulty (diesel engines);
• air in the fuel system (diesel engines);
• mechanical failure of the valve timing system.

Unstable cold engine starting

• battery is low;
• the battery terminals are not securely connected or are oxidized;
• failure or incorrectly adjusted interelectrode gaps in spark plugs (gasoline engines);
• the pre-heating system is faulty (diesel engines);
• the fuel injection system is damaged (gasoline engines);
• ignition system damage (gasoline engines);
• low compression in cylinders.

Unstable hot engine starting

• the air filter element is dirty;
• fuel injection system damage (gasoline engines);
• low compression in cylinders.

There are extraneous noises when the starter is turned on

• worn or broken teeth on the starter pinion or flywheel ring gear;
• starter mounting bolts are missing or not tightened securely;
• wear or damage to starter parts.

Engine stops after starting

• unreliable connection of ignition system components (gasoline engines);
• air leak in the injection system or intake manifold (gasoline engines);
• fuel injection system damage (gasoline engines).

Unstable idling of the engine

• the air filter element is dirty;
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• the interelectrode gap is incorrectly adjusted or the spark plugs are worn out (gasoline engines);
• uneven or low compression in the cylinders;
• camshaft cams are worn out;
• the timing belt is not installed correctly;
• fuel injection system damage (gasoline engines);
• the injectors are faulty (diesel engines).

Misfires at idle

• the interelectrode gap is incorrectly adjusted or the spark plugs are worn out (gasoline engines);
• defective high voltage wires (gasoline engines);
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• fuel injection system damage (gasoline engines);
• the injectors are faulty (diesel engines);
• uneven or low compression in the cylinders;
• the engine crankcase ventilation hoses are disconnected or leaky.

Misfires throughout the entire engine speed range

• the fuel filter is dirty;
• fuel pump faulty or low fuel pressure;
• the fuel tank drain hole or fuel lines are clogged;
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• the interelectrode gap is incorrectly adjusted or the spark plugs are worn out (gasoline engines);
• the ignition coil is faulty (gasoline engines);
• the injector is faulty (diesel engines);
• distributor breaker cover is faulty (gasoline engines);
• uneven or low compression in the cylinders;
• fuel injection system damage (gasoline engines).

Engine vibration when accelerating

• the interelectrode gap is incorrectly adjusted or the spark plugs are worn out (gasoline engines);
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• fuel injection system damage (gasoline engines);
• the injector is faulty (diesel engines).

Unstable engine operation

• air leak in the injection system, intake manifold or hoses (gasoline engines);
• the fuel filter is clogged;
• malfunction or low fuel supply pressure of the fuel pump (gasoline engines);
• the fuel tank drain hole or fuel lines are clogged;
• fuel injection system damage (gasoline engines);
• the injectors are faulty (diesel engines).

View the original on the website (PEUGEOTBOOK)

Low engine power output

• the timing belt is not installed correctly;
• the fuel filter is clogged;
• fuel pump faulty or low fuel pressure;
• uneven or low compression in the cylinders;
• the interelectrode gap is incorrectly adjusted or the spark plugs are worn out (gasoline engines);
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• fuel injection system is faulty (gasoline engines);
• the injectors are faulty (diesel engines);
• fuel injection timing of the fuel pump is set incorrectly (diesel engines);
• brake sticking;
• clutch slippage.

Backfires in the engine

• the timing belt is not installed correctly;
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• fuel injection system damage (gasoline engines).

Low engine oil pressure

• low oil level or wrong grade of oil;
• the oil pressure sensor is faulty;
• engine bearings or oil pump are worn out;
• engine overheating;
• oil pressure relief valve is faulty;
• the oil receiver mesh filter is dirty.

The engine runs after the ignition is turned off

• excessive carbon deposits in combustion chambers;
• engine overheating;
• fuel injection system damage (gasoline engines);
• the electromagnetic engine stop valve is faulty (diesel engines).

Engine noises

Engine detonation during acceleration:

• the ignition timing is set incorrectly (gasoline engines);
• spark plug type does not match required;
• low octane fuel;
• air leak in the injection system, intake manifold or hoses (gasoline engines);
• excessive carbon deposits in combustion chambers;
• fuel injection system damage (gasoline engines).

Whistling or wheezing noises:

• intake manifold or throttle body gasket is leaking (gasoline engines);
• exhaust manifold gasket leaking;
• vacuum hoses are leaky;
• the cylinder head gasket is blown.

Rattling noises:

• the valve mechanism or camshaft is worn out;
• wear of auxiliary engine components (water pump, generator, etc.).

Detonation or dull noises:

• the lower connecting rod head bearings are worn out (noise decreases under load);
• main bearings are worn out (noise increases under load);
• piston strikes (especially on a cold engine);
• engine auxiliary components are faulty (water pump, generator, etc.).