Engine starts with difficulty It is highly probable that the spark plugs are the culprits when you start your car early in the morning, and you have to crank up the engine several times.
Idling roughly When your car is idling in good conditions, the sound should be a nice smooth and consistent sound – a pure engine sound. If you notice irregular and loud sounds, the spark plugs are most probably the ones to be blamed.
Misfires Poor plugs will not help the cylinder to fire up properly and will cause misfires. Misfires can be dangerous to your car as they can destroy a coil or cause the cylinder to overheat, which will result in damaging the valve or the piston. And, you don’t want that to happen!
Poor Acceleration When you accelerate to move away from a traffic light and you can hear the car choking like an asthmatic, and everyone’s attention is attracted by your car’s dreadful sound – you know it – your spark plugs.
Poor Fuel Efficiency You don’t want your old spark plugs to affect your engine performance and fuel efficiency. Spark plugs won’t last forever. The common copper ones last between 10,000 to 20,000 miles. Platinum will let you drive around 50,000 to 60,000 miles and Iridium for a further 100,000 miles. At a time when you notice you are getting less mileage from each gas tank refill, it could be time to change for a fresh set of spark plugs.