When Should You Replace Spark Plugs?

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Spark plugs are very important parts of any car with a gasoline engine. From the name itself, it creates an electrical spark which ignites the air-fuel mixture that is present in the combustion chambers of the engine. Without this electrical spark, the air-fuel mixture will not “explode” and the engine will not be able to produce the necessary force to push the pistons up and down the cylinders so that they, in turn, will turn the crankshaft. While your vehicle owner’s manual will tell you when you have to replace the spark plugs in your engine, the figure stated in the handbook is more of a guide. So, how else will you know if it’s time to replace these parts of your car?

spark plugs

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Check the Manual

If you have been judiciously following the recommended maintenance schedule of your vehicle according to your vehicle manual, then it is best to adhere to the recommended schedule of spark plug replacement. If the manufacturer says you need to replace the spark plugs every 30,000 miles, then you should follow it. However, take note that the recommendation is generally applicable to the type of spark plug that the vehicle manufacturer put into your engine when you bought it. Unfortunately, if you have an entirely different type of spark plug, then the recommendation may not really be spot on.

For instance, high performance spark plugs typically have electrodes that wear out a lot faster than conventional or stock spark plugs. As such, these may have to be replaced sooner or more frequently than the stock ones. There are also spark plugs that are designed to be longer-lasting. These often come with electrodes that are more durable than high performance spark plugs. For example, platinum and iridium spark plugs last longer than copper spark plugs.

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You also need to consider your driving habits. If you’re the kind of person that loves revving up your engine, then you’ll know that your spark plugs will wear down a lot faster. If you’re driving sensibly or are light on the pedal, then you can even outlast the lifespan of your spark plug.

Signs that You May Need to Replace Your Spark Plug

As already mentioned, there will always be situations when your spark plug wears down a lot faster than expected. This phenomenon can be related or attributed to a host of factors. You can perform daily inspection of your spark plugs, why not? But this can be very tedious. As such, you have to familiarize yourself with some of the most common signs that your spark plug may already be nearing its end.

Problems Starting the Car

There are many reasons why a car may not start. It could be because of a dead battery, there’s no fuel in the tank or in the fuel chamber, or even a faulty alternator. More often than not, however, is that the problem is in the spark plug. If you can manage to turn on the electrical components of your car such as the lights, the stereo, and others, but cannot seem to crank your engine, then your problem is a damaged or failing spark plug. It simply isn’t creating enough ‘spark’ to ignite the air-fuel mixture in the combustion chamber.

Rough Idle

We all want our engine to be purring like a kitten, hopefully not literally, especially when our cars are at a standstill. But the point is that we should hear a sound that is music to our ears and not one that rumbles, pings, rattles, or even knocks under the hood. In addition to the noise, you may even feel vibrations in the steering wheel, if not the entire car. While there are also other potential causes of rough idling, one of the more common causes is a problem with the spark plug. The jittery sound is usually brought about by the inconsistent firing of the spark plug. You may have to replace it soon enough.

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Engine Misfires

The principal job of the spark plug is to ignite the fuel-air mixture in the engine so that controlled explosions can be obtained. This has to occur at a very precise moment. As always, spark plug failure is not the only cause of engine misfires. It can also be caused by problems in the spark plug wires, issues in the fuel-delivery system, or even wiring or computer problems. However, since gaining access to your spark plug is a lot easier and less expensive than the other potential causes of engine misfires, replacing your spark plug when your engine misfires seem like a worthy place to start.

Problems with Acceleration

If the spark plug is not consistent in delivering an electrical arc to the fuel-air mixture, you may also notice that your vehicle may have a more difficult time accelerating. This is because there’s not enough “controlled explosions” occurring inside the combustion chamber. You may find you’ll have to depress the gas pedal a lot more for your car to accelerate at the ‘usual’ rate. Your car will be quite sluggish. Replacing the spark plugs may be your answer to such woes. Of course, there are other possible causes of poor acceleration, but it would be wise to also consider the spark plugs.

Poor Fuel Economy

According to the National Institute for Automotive Service Excellence, spark plug problems such as misfires can reduce fuel economy by up to 30 percent. Your engine will need more fuel to produce the same amount of energy that it normally produces with a normal, fully-functioning spark plug. Problems in the spark plug simply mean your engine is not burning fuel on a more efficient manner. So you will find yourself driving into your favorite local gasoline station more often than you used to.

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Spark plugs are very important pieces to the optimum operation of your engine. They are relatively inexpensive and very easy to replace. While adhering to the recommendations of the vehicle owner’s manual can help you determine when you should replace your spark plugs, it is equally important to be aware of the possible signs of spark plug issues.


  1. How Spark Plugs Work – howstuffworks
  2. How to Change Spark Plugs – wikiHow

Originally posted 2023-01-20 18:10:09.

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