Spark Plug


Spark Plug

A spark plug is a device that transforms electrical current from an ignition system into hot sparks that ignite the air/fuel mixture inside an engine. Except for some luxury and exotic vehicles, there is usually one spark plug per cylinder. This means if you have a six-cylinder engine, you’ll need six spark plugs for its operation. 


Just like many other parts in your vehicle, spark plugs require routine maintenance and regular replacements. Depending on the material it is made of and the condition of your engine, your spark plugs may last from 2000 to 100000 miles and even more. 

Each of your spark plugs sits in the cylinder head of your engine, protruding into the combustion chamber. If you could look at a spark plug from the inside of your engine, you would see the end of its central electrode and a porcelain insulator. The other components of a spark plug are a threaded metal casing and a ground electrode. 

When the engine is running, your ignition system sends high voltage to the center electrode. This voltage jumps the gap between the central electrode and the ground one, creating a spark. This spark ignites the already compressed air/fuel mixture inside a cylinder, causing an explosion that pushes the piston down. 

If one of your spark plugs fails to create sparks, you’ll experience a variety of engine problems, including the following ones:

Your check engine light is on or blinks

A failed spark plug will cause misfires in one of the cylinders. Since the engine control unit monitors all misfires and backfires in the engine, it will turn on the check engine light once the problem is found. In some cases the check engine light may blink, which says that a more severe problem, like damage to your catalytic converter, may occur. 

Rough idling and lots of vibration 

A faulty spark plug will either not ignite an air/fuel mixture at all or do this improperly. Whichever happens, your engine will misfire, causing rough idling and abnormal vibration you will be able to feel in the cabin of the vehicle.

Poor acceleration

In some cases, you may experience poor acceleration when there are no other signs of bad spark plugs. This may happen because spark plugs are prone to wear and tear over time. Under normal conditions, they wear all together, slowly affecting your performance and acceleration. 

Increased fuel consumption

Misfires caused by one or more faulty spark plugs lead to wasting fuel. You’ll need to push your accelerator harder, so the other spark plugs could compensate for the lack of power. As a result, more fuel will be burnt per mile. 

Your car is harder to start

A poor spark plug can’t ignite an air/fuel mixture with the first or second spark as they are weak. That’s why your starter will have to crank the engine longer to start the combustion process.

There is a ticking noise from under the hood

A low-quality or worn-out spark plug can crack. If so, it may begin to leak, allowing combustion gases to release into the air, which is accompanied by a ticking noise.

Foul smells from the tailpipe

If combustion doesn’t occur due to a faulty spark plug, raw fuel will enter the exhaust system. As a result, you’ll notice a smell similar to rotten eggs.

Spark plug maintenance

To keep your engine running properly, the spark plugs must be replaced at the mileage and time intervals mentioned in your owner’s manual. Besides, if you’re not satisfied with the quality or condition of your spark plugs, you should replace them with new ones. It is also very important to check the recommended spark plug gap between the electrodes. For this purpose, you can use a special measuring tool or leave this job to a mechanic. 

Except for some vehicles that feature two spark plugs per cylinder, replacing spark plugs is a simple and not time-consuming task taking into account that your spark plugs are easy to access. If not, you should call your mechanic for advice.

Can I replace spark plugs myself?

This is a regular maintenance task most of us can handle without professional assistance. However, you should follow several simple rules to have the job done properly. Be sure to use the same quality spark plugs as your OE ones that are also of the same size and length. 

Take off and install spark plugs with a special torque wrench to prevent over-torqued spark plugs. It is also a good idea to add some anti-seize compound on spark plug threads for their easy removal next time. Keep in mind that spark plug wires should also be replaced along with spark plugs.

Once your spark plugs are removed, don’t hurry to throw them away as their color and condition may tell you a lot about your engine operation. If the spark plug’s electrode is white, it says you have a lean mixture or your engine overheats. A black electrode is a sign of a rich air/fuel mixture. If your spark plugs are wet, most likely fuel isn’t burned completely in the cylinders. A heavy black residue on spark plugs is the worst case scenario as this means excessive oil enters the combustion chamber.

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