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Spark Plug Replacement Cost: 2022 Guide | 5 Symptoms Inside

Your car’s spark plugs are critical pieces of the ignition system, and they are crucial when it comes to proper operation of your engine. Just like other car parts, your spark plugs will eventually wear out. The constant heat and electrical current that your spark plugs endure will cause them not to produce a spark like they once did. So, what happens when you need new spark plugs? How much will it cost you, and can you swap them yourself? We will give you all the details about spark plug replacement, including how much it will cost and how to do it yourself.

Spark Plug Replacement Cost — How Much Is It?

Several factors affect the cost of this car repair. The first is the size of your engine. Since your engine has a spark plug in each cylinder, larger engines will require more spark plugs than smaller ones. The labor costs will also be higher for larger engines since the mechanic will need to swap out more spark plugs. Finally, the type of spark plug that your vehicle requires will have an impact on the cost. High-end cars usually require more expensive spark plugs.

The average cost to have an automotive repair shop replace your spark plugs is about $200. If you take your car to your dealership, your bill is likely to be closer to $300. Spark plugs cost only about $8 each, so you can see that you are likely to save money by performing the job yourself. Spark plugs are rarely covered under warranty unless there is some defect, and they are considered a maintenance item, much like an oil change or tire rotation.

What Is A Spark Plug & How Does It Work?

A spark plug is a device that provides the spark inside your combustion chamber to ignite your air-fuel mixture. The spark plug is connected to your car’s ignition system using spark plug wires. Your engine has a spark plug in each cylinder. So, if you have a four-cylinder engine, then you will have four spark plugs. Similarly, a V-8 would have eight spark plugs. So, what do spark plugs do?

The ignition system sends an electrical current through the spark plug wire to the spark plug when a specific cylinder should fire. The current travels through the electrode in the spark plug, and a spark is produced in the spark plug gap as the current jumps from the center electrode to the ground electrode. When this spark occurs, the fuel mixture in the combustion chamber ignites, and that cylinder fires.

While this sounds relatively simple in theory, remember that this process is happening incredibly quickly. Your spark plug may be firing thousands of times each minute. Also, note that some newer vehicles have ignition coils attached directly to your spark plugs. Instead of a central distributor with spark plug wires going to each plug, an ignition coil attached to each plug directly controls the spark there. The plugs are screwed into your cylinder heads, with the electrodes coming through into the combustion chamber.


Symptoms Of Bad Spark Plugs

So, how do you know when your spark plugs need replacing? Most of the time, your car will make you aware that your plugs are getting old. Here are some things to watch for.

— Check Engine Light

One of the first warning signs of bad spark plugs is often a check engine light. When you see this light on your dash, it is often because your engine is not firing correctly. Old spark plugs that are firing thousands of times per minute are likely to misfire occasionally. When this happens, your car’s computer is smart enough to detect those occurrences. If you see a check engine light, then take your vehicle to your local repair shop. Most shops and auto parts stores will read this code for you at no charge to help you determine whether the spark plugs are the likely culprit.

— Engine Misfiring

You might start to notice that your car’s engine performance is declining. Misfires in your engine will cause it to feel like your engine is stumbling or skipping as you accelerate. If you start to feel this happening, then it might be time for new plugs. Sluggish performance could also be caused by other things like a clogged fuel filter or a bad catalytic converter, so it is an excellent idea to let a repair shop diagnose your specific problem.

— Poor Fuel Economy

The computers in today’s cars allow them to run highly efficiently. The precise amount of fuel necessary for your vehicle is sprayed into each cylinder, and your spark plugs fire at the exact moment the spark is needed. However, when your plugs get old and no longer work as they should, you can start to see the effects on your fuel bill. Your vehicle might be dumping more fuel than necessary into the combustion chamber because the lack of a proper spark fools the computer into thinking that the car requires more fuel. If you notice your vehicle burning more gas, then you might consider swapping your plugs.

— Rough Idling

When your car idles, it should be nice and smooth. However, old plugs might be the culprit if you notice that your vehicle is shaky and your RPM gauge bounces a little at idle. Poor spark or lack of spark will cause your engine to run rough at idle, and you will undoubtedly feel it while sitting at red lights or parked in other places. A tune-up with a fresh set of spark plugs is likely to fix this problem.

— Hard Engine Starts

If you turn the key and your car won’t start, then your plugs could be to blame. Most of the time, bad plugs will make it harder for your vehicle to start. You may notice that your engine turns over for a little longer before finally starting up. If your engine is not getting the proper spark, especially when it is first started, it will be harder for it to crank. Go ahead and visit your auto repair shop to have your plugs checked.

How Often To Replace Your Spark Plugs

Many people wonder when to change spark plugs. Thankfully, spark plugs are designed to last for quite some time. It would be best if you referred to your owner’s manual for your car’s specific maintenance schedule, but most spark plugs today will last at least 75,000 miles. These spark plugs are usually made with platinum or iridium. Standard spark plugs might need to be changed every 50,000 miles. Since most people only keep their vehicle for a few years, you might never even need to change the spark plugs in your car.

Cheap gas can also cause you to replace spark plugs more often, and low-quality gasoline can cause build-up inside your engine that will foul out your spark plugs. Make sure that you always use high-quality gas in your vehicle to avoid these problems.

Do It Yourself Steps To Spark Plug Replacement

This is a vehicle repair that many people choose to complete on their own. Not only can you save money on a spark plug change, but it also gives you an incredible feeling of accomplishment when completed. Many people wonder how to change spark plugs, and the task of changing spark plugs is not difficult. First, you should gather the necessary tools and supplies. You will need your new spark plugs along with a torque wrench and spark plug socket. A socket extension will likely be required as well.

First, locate the spark plugs in your engine. They will be located near the cylinder heads and intake manifold. Start by removing the spark plug wire or ignition coil and then the spark plug itself. It is a good idea to work on one at a time not to get the wires in the wrong location. Once the old plug is out, then you can go ahead and reinstall the new spark plug. Place a small amount of anti-seize on the threads for easier removal next time. Make sure that you use a torque wrench and do not over-tighten! Place a small amount of dielectric grease on the terminal and reconnect the wire. Complete these steps for each spark plug, and you are all done!

The Bottom Line

Spark plug replacement is a job that you might decide to tackle yourself, but if not, most repair shops will perform the task for around $200. Your spark plugs will generally only need to be replaced about every 75,000 miles, so this is not something that you will need to worry about often. If your car is getting a lot of miles or you notice any of the symptoms described in this article, then you might want to consider getting a spark plug replacement soon.

Frequently Asked Questions

Can I replace my spark plugs myself?

Absolutely! Spark plug replacement is not a highly complex process for most vehicles. You need to remove the old spark plugs and reinstall the new ones. Ensure that you do not over-tighten the new plugs, and work on one at a time to avoid replacing any spark plug wires in the wrong spot. Doing this will cause your engine to run very rough or maybe not even crank at all.

How do you know when it’s time to change your spark plugs?

If your car has been idling rough or you have a check engine light, then it is probably time for spark plugs. Even if you have not yet noticed any symptoms of bad spark plugs, you should still go ahead and replace them if your car has more than 75,000 miles. Some spark plugs might need replacement more quickly, but your owner’s manual should give you additional details on the interval for your vehicle.

What are the benefits of replacing spark plugs?

Replacing spark plugs will cause your car to run more smoothly and efficiently. In addition, you might even see an increase in your fuel economy. Performing regular maintenance on your vehicle, including spark plug replacement, is crucial to keeping your car running well for years to come.

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