Why you should change your spark plugs
Spark plugs need to be maintained properly if the engine is to operate smoothly. Neglect them and you could experience several issues.
First, you may find it difficult to start the engine. You’ll have to turn it over several times before it fires and this may flatten the battery over time. Once the engine is running, it may have a rough idle and feel ‘lumpy’ or it may misfire, which indicates that not all cylinders are working as they should. Misfiring should be sorted immediately, because you risk damage to the catalytic converter, which is expensive to replace.
A faulty spark plug may also cause increased fuel consumption and a reduction in engine power, and should be investigated at your earliest opportunity.