What do spark plugs do?
Spark plugs convert electric current from the ignition coil into a spark that ignites the fuel and air mix inside the car engine. This combustion is what powers the engine and moves the car. Spark plugs are located in the cylinder head and are connected via external leads attached to the engine.
How often should spark plugs need replacing?
Most manufacturers recommend that spark plugs should be replaced at around every 30k miles; this is only a guideline, as the quality of the component, engine performance and driving habits can affect spark plug lifespan significantly.
The law, vehicle regulations and your MOT
Old or damaged spark plugs can affect engine performance areas that cause an MOT failure, for example, in emissions testing. Poor performing spark plugs or filters that clog up can affect the gasses that are delivered from your exhaust; replacing these faulty parts can often rectify the problem.
What causes spark plugs to stop working correctly?
Spark plugs can wear out over time, at which point they should be replaced to ensure the correct combustion of fuel. There is also a chance of potential carbon build up on the electrodes; this is known as carbon fouling and will affect the correct operation of the spark plugs. Oil can build up on the spark plugs too, which can be rectified with a simple cleaning.
Spark plugs can occasionally melt due to excessive engine temperatures. This isn’t usually a spark plug fault, but that of the engine or fuel system.
Symptoms of malfunctioning spark plugs
Starting your engine is problematic
If your car struggles or fails to start, it could be down to faulty spark plugs.
Engine cut out or misfiring
If your engine cuts out after starting or during its usual operation, if it fails to run smoothly or it vibrates excessively under normal use, then your spark plugs could be due to worn out spark plugs.
The dashboard engine warning light is illuminated
Any dashboard warning light is due to a sensor detecting fault or incorrect operation of a related component. An engine warning light could relate to a faulty spark plug.
Fuel consumption is higher than normal
Faulty spark plugs can cause your engine to burn fuel in an erratic manner, affecting both vehicle performance and fuel consumption. If you notice a change in your fuel consumption, it could be a spark plug problem.