For those who want to begin maintaining and working on their own vehicles, spark plugs are a great place to start. These small parts are critical to the operation of any vehicle, yet they're simple to both understand and replace. It's a good first job for someone to take on if they've never done any auto maintenance on their own before.
The key to a spark plug is right there in the name - it provides a spark for the engine. Car engines are also called "combustion engines" and the spark plug is what ultimately makes the fuel combust. A high voltage is electric signal is generated by a coil in the ignition system, which then travels to the spark plug. Spark plugs function by making a small gap that the electricity needs to jump through. If the electricity is of high enough voltage, it will arc across the gap and cause a spark. In this way, spark plugs can be thought of as trapping lightning in a bottle - or in this case, a combustion chamber.
When the electricity arcs across the gap, the idea is to ignite the compressed fuel and air mixture that is in the combustion chamber. This small explosion generates the pressure that moves the pistons and gets the engine to start moving. Obviously, this demonstrates that a malfunctioning spark plug can in turn decrease engine performance and cause other problems in a vehicle. In the old days, a car with non-working spark plugs would not be able to run at all. Today's new vehicles are a bit more resistant to failing outright, but spark plugs are still very important to pay attention to.
The other reason that it's important to learn about spark plugs is that it's a good diagnostic tool for other vehicular problems. For example, a spark plug that is covered in black gunk probably indicates that you have an oil leak somewhere, which needs to be taken care of right away. A spark covered in black soot could indicate carbon deposits building up in your vehicle. White spark plugs indicate that your engine is running too hot, and the cooling system may not be doing its job. And finally, if the spark plug appears damaged as if it has been blown up, your engine could be misfiring due to improper fuel or perhaps excessive modifications made to it.
Replacing spark plugs is simple and can help increase the performance in your vehicle. The most important thing to keep in mind while doing this is that the spark plugs have a specific firing order, and you can't cross the wires in the vehicle. When you disconnect the wires, label them to match the corresponding plug so nothing gets mixed up. Be careful when removing the wires, as they are a more expensive replacement than the plugs themselves.
You'll most likely need a ratchet and corresponding socket in order to loosen the spark plugs enough to then untwist them by hand. It's then simply a matter of taking your replacement spark plugs and inserting them where the old ones used to be. Remember, it's best to do this one at a time so you don't confuse the wiring. Screw the replacement spark plugs in by hand, but be sure to tighten them with a wrench, as loose spark plugs may malfunction.