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The spark plug

The spark plug is responsible for delivering the spark necessary to trigger the combustion of the air-gasoline mixture. Indeed, it is the quality of the spark that will determine the fuel consumption as well as the power and flexibility of your engine.

Spark plugs have a service life of 30,000 to 120,000 km. Have them checked every 30,000 km and pay attention to the operation of the engine. When a spark plug is faulty or worn, the engine continues to run but it misfires. Consequently, the car loses recovery and over-consumes. Over time, your spark plugs wear out and clog up. The performance of your engine decreases: you pollute more, you consume more and your catalytic converter clogs!

Good to know: The spark plug is a highly stressed part: 1500 sparks produced per minute, for an average engine speed of 3000 rpm. It undergoes a combustion temperature of around 2500°C!

For an engine speed of 4,000 rpm, the spark plugs produce 2,000 sparks/min and experience a combustion temperature of approximately 2,500°C. When changing them, it is therefore advisable to scrupulously respect the thermal index provided by the manufacturer.

When replacing the spark plugs, respect the thermal index recommended by the manufacturer.

Why change your spark plugs?

A failing spark plug will cause these failures:

Decline in engine power, Overconsumption of fuel, Polluting engine.

When to change spark plugs?

The Volkswagen brand recommends replacing spark plugs every 40,000 kilometers. With other manufacturers, this can vary from 30,000 km to 50,000 km.

To avoid ignition imbalances, we advise you to replace all the spark plugs, even if only one is faulty.

Check the wear of your spark plugs:

If your spark plug is damaged, the spark plug head will be a little dirty. If you find a whitish scale deposit on your spark plug around the electrodes or even burn marks, this means that it must be replaced.

Similarly, if you observe a deposit of soot on your spark plug, it is necessary to change the spark plug.

If you've done the recommended miles and none of these are detected, change them anyway, as they will soon wear out.

Check the gap between the electrodes: the clearance value should be between 0.71 and 1.52 mm. If the gap between the electrodes of one of your spark plugs deviates from these values, they should be adjusted. If the end of the candle is broken or cracked, go no further and buy another one

How to replace spark plugs?

Tools and equipment needed:

Candles (make sure they are exactly the same as the old ones). A spark plug wrench, A rag or brush, Gloves, An electrode gap gauge, Long-nose pliers


Nowadays, the ignition system requires virtually no intervention; in fact, it replaces all capacitors and breakers, and is managed automatically by the engine management computer. Below are listed the other components of the ignition system:

The coil

It transforms the battery voltage into high voltage current: from 12 V to 25,000 V

The ignition harness (or High Voltage harness)

Several systems are used to transmit the high voltage current: A mechanical electrical distribution system with an igniter head or distributor, a system equipped with an electronic ignition module, and finally an ignition system with ramps or pencil coils controlled directly or indirectly by the injection computer.

Have it checked every 50,000 km: a worn harness leads to electrical leaks which can disturb the electronic components of your car as well as the catalyst.



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