Spark Plugs

What are spark plugs and where are they located?

Spark plugs are a relatively simple but integral part of your car or truck’s ignition system. They carry high voltage electricity into each cylinder head to create a spark that ignites the compressed air-fuel mixture inside, resulting in combustion—which is what ultimately powers your automobile. They also act to transfer heat away from the combustion chamber to the engine’s cooling system.

The power needed to make the spark plug work is initially generated by the vehicle’s battery upon startup. The spark plug receives its power either directly from a distributor or an ignition coil via a spark plug wire that connects to the spark plug terminal (or connecter) at the top of the spark plug. The charge then travels through a central, metal conductor (or core) covered by a ceramic insulator.

When the bottom half of the spark plug is threaded into the cylinder head, a small electrode on the end of the spark plug is connected to a metal shell that grounds into the engine block. The core’s tip, which protrudes out of the bottom of the ceramic insulator, also acts as an electrode and is known as the center electrode. Electricity arcs across the gap between the two electrodes, creating the spark needed to ignite the air-fuel mixture during the compression stage.

As a side note, spark plug wires are not used in newer vehicles that have coil-on-plug setups considering each cylinder has its own coil (usually bolted to the valve cover on top of each spark plug) to transfer the current directly to the plug via a coil boot. However, in most vehicles, the spark plugs and wires are arranged according to the engine cylinders' correct firing order sequence. Current is transferred to each spark plug wire according to this specific sequence, allowing for proper ignition spark at just the right time for the engine to start and the vehicle to move. Proper spark plug functioning is essential to proper ignition.

The number of spark plugs found in a car or truck varies depending on the engine in the vehicle. There are also different types of spark plugs available. A standard plug has a copper center electrode core surrounded by a nickel alloy, seen at the end of the plug. There are also premium spark plugs available, which make use of precious metal such as platinum or iridium, rather than the nickel alloy.

How do I know if my spark plug needs to be replaced?

Due to their location, spark plugs are exposed to extremely high temperatures and forces as well as other effects of combustion. They are, of course, designed to withstand these pressures, but can be expected to eventually wear down. The time this takes will vary from one spark plug to another, but 20,000 to 30,000 miles is a common lifespan for copper plugs. Performance plugs made of different metals like platinum or iridium can last much longer. 

Since a bad spark plug will affect ignition in its cylinder, it will often result in poor engine performance. This may manifest as rough idling, hesitation or surging during acceleration, a pinging or knocking noise coming from the engine, engine misfires, or worst of all, a complete failure to start the engine. 

It may be possible to identify the source of your problem by visually inspecting the spark plug. This may point to a deeper problem that has caused your spark plug failure. It is typical to find the end of the plug has turned a light brown color, but sooty or ashy carbon deposits can be a sign of an overly rich fuel-air mixture. Melted electrodes can signify that pre-ignition is occurring, combusting the fuel too early. A cracked ceramic insulator indicates engine overheating or fuel detonation (knocking). Mechanical damage to the spark plug might mean that it was installed improperly or there is some sort of foreign material in the cylinder. 

Can I replace a spark plug myself?

Considering the limited life of a spark plug, it’s fortunate that replacing them is relatively easy on most engines. They are found in the cylinder head on top of the engine block making them often easy to access. You may have to remove an engine cover to reach them. In some cases, such as front-wheel drive (FWD) V6 engines, they may be harder to reach and you may have to remove parts of the air intake system or other parts to access them. 

There are a couple steps you can take to ensure that your spark plug replacement goes smoothly. The spark plugs have a specific firing order that must be maintained for the engine to work properly. For this reason, it is best to replace the spark plugs one at a time or to label the spark plug wires with tape and a marker to ensure they are replaced in the correct order. Before installing the new spark plugs, you will need to consult your owner’s manual to determine the correct torque to tighten the spark plug hex nut to in order to avoid damaging it, and the correct gap between the electrodes so that they spark properly. In order to measure that gap you will need a tool known as a spark plug gapper. Applying anti-seize grease to the threads will help you more easily remove the spark plugs next time you replace them, but be sure not to get the grease on the electrodes as it may make them fail to fire. 

Need a spark plug replacement?

To put it simply, a failed spark plug will result poor engine performance, which can manifest in a variety of ways including the inability to start it. Of course, being unable to start your engine means your car or truck isn’t going anywhere. Therefore, making sure you replace your spark plugs as required, and as soon as possible if they have failed, is critical to proper vehicle operation. Luckily, 1A Auto has that “spark” that you need. We carry aftermarket spark plugs, including performance spark plugs made of iridium or platinum metal, for many makes and models, and at great prices.

At 1A Auto, we make shopping for replacement spark plugs for your car, truck, SUV or van easy - we're here to help you select the right part for your vehicle! Call our customer service toll free at 888-844-3393 if you have any questions about our aftermarket spark plugs, warranty, compatibility or to purchase, or you can buy online.