Everything You Need to Know About Spark Plugs

Sometimes, the most important things are ignited by a single spark. When it comes to a vehicle's engine, it needs a way to fire - and yes, it's much more complex than putting your key in the ignition and turning it. Engines need a spark of electricity to ignite, and that's why spark plugs are so important in cars. Spark plugs in good condition help an engine start without any problems whatsoever. Conversely, spark plugs that are in poor condition may prevent the engine from turning over altogether. This post will take a closer look at spark plugs and describe how they work, when to change them, and what the best brands to buy are.

Spark Plugs: The Basics

Spark plugs are a very small, basic automotive part. They fit onto the cylinder head of the engine and work to ignite the air/fuel mixture present in the engine so that it fires, thereby allowing the operator to drive the vehicle. After all, if the engine won't turn over, the vehicle is basically useless. Spark plugs are only an inch or two in size, but they pack a lot of purpose into them. They contain the likes of electrodes, wires, ignition coils, and circuits, all of which work together to transmit electrical energy to ignite the engine in its combustion chamber.

Spark plugs help ignite the engine.

Aside from helping to ignite the engine, however, spark plugs also serve another key purpose: heat transmission. Yes, the other main function that spark plugs perform is moving heat away from the engine's combustion chamber. They do this by moving unnecessary heat from the engine's combustion chamber and into its cooling chamber.

How many spark plugs does the conventional vehicle have? It all depends on the engine. For example, a car with a four-cylinder engine will have four spark plugs - one for each cylinder. A car or truck with a V6 under its hood will have six spark plugs - and so on.

When to Change the Spark Plugs

Spark plugs that are in good condition are crucial to a well running engine. But it's also important to remember that spark plugs endure automotive extremes based on where they are placed (i.e., the engine cylinders), the high temperatures they work under, and the thousands of times they may be tapped to help start the engine. As you might imagine, it's not uncommon for spark plugs to reach a point where they need to be changed to ensure an effectively operating vehicle. Most automakers recommend changing out the spark plugs every 30,000 miles, which is one key milestone to note when it comes to changing these components. Here's a look at some other signs and symptoms that your vehicle's spark plugs might be on the fritz:

    • Hard starting: Because spark plugs work in such demanding conditions, they'll become dirty or soiled over time. When this happens, there's going to be an impact in how effectively they perform their job. This often leads to hard starting, especially in the morning after the vehicle has been sitting overnight. The dirtier and more heavily soiled the spark plugs are, the more difficult it's going to be to start your vehicle. What's more is soiled spark plugs could even be draining more power from your car battery. A misfiring engine or an engine that won't start at all could also be a sign of bad spark plugs.
    • Rough idling: If your car starts, but it seems like it's idling roughly, take note. The issue could very well be faulty spark plugs. Spark plugs are designed to provide a consistent energy supply for your vehicle by way of the engine. If it's idling roughly, there may be some issues with this.
    • Your fuel economy is sagging: If you seem to be filling up your gas tank more often than before, make sure you track your mileage and miles per gallon between fill ups. Bad spark plugs can reduce fuel economy by up to 30 percent.
    • Poor performance: If your vehicle seems to hesitate when you press down on the accelerator pedal or you're noticing just a significant lack of acceleration when you're asking for it, checking out the condition of the spark plugs should be part of the inspection that you perform on your vehicle to resolve the issue.

How to Change a Spark Plug

Though changing a spark plug isn't as easy as some other basic automotive maintenance tasks, it can be done, and it can shave some significant labor fees off of your trip to the mechanic. Changing a spark plug takes about an hour to do on a four-cylinder engine.

Seized spark plugs are difficult to remove and replace.

Here's a brief overview of the process:

    • Prep: Move out any hoses or components that are interfering with your access to the engine. Then clean around the engine, especially on its head.
    • Pull up on the locking tab of the ignition coil electrical connector to disconnect it.
    • Find the coil hold-down bolt and remove that. This will remove the entire boot assembly, where you'll then be able to see the old spark plug.
    • Remove debris from around the old spark plug. Next, unscrew it with a socket wrench. (A swivel socket makes this step go much faster.)
    • Using a gap gauge, you need to check - and perhaps adjust - the spark plug gap before installing it.
    • Once the gap is set, use a torque wrench and install the new plug. Make sure you're following the automaker's recommendations for best results.
    • Place a drop of lube in the boot, and then reassemble the boot and reconnect the ignition coil.

Best Spark Plugs to Buy

When it comes to quality spark plugs, it's all about material. A better, more durable material, for example, can mean a longer lasting product (not to mention one that works better too.) Here's a look at some of the top brands and spark plugs:

    • AC Delco: This long-time automotive supplier is well known for its spark plugs, and its Professional Iridium plug is one of its most well-known. It's affordable yet durable and it is a good middle-of-the-road option for vehicle owners.
    • Bosch: Bosch's Platinum IR Fusion Spark product is an affordable plug that can help improve engine performance and efficiency.
    • NGK: NGK's Iridium IX is ideal for power vehicles. They're designed to be corrosion-resistant and are designed to improve fuel economy.
    • Autolite: Autolite's APP104 Double Platinum plug is very durable, resistant to corrosion and is also designed to provide a performance boost.