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The fundamental operation of all internal combustion engines involves injecting a combination of fuel and air into the combustion chamber, where the spark plug ignites it. The explosion will force the pistons to move down, which turns the crankshaft and moves the vehicle. Of course, many other components are involved in turning the wheels, but it takes a little spark to make it all happen.
In this article, I will explain what a spark plug is, the warning signs of a problem with the spark plugs, and the cost of changing the spark plugs.
What is a spark plug?
To understand a spark plug, visualize a tiny but powerful lightning bolt. With each bolt of lightning, an explosion of fuel and air is ignited in your engine's combustion chamber. Now, visualize this across multiple engine cylinders, and you have a good idea of what makes your engine tick. With the technology in vehicles today, the chance of a spark plug going bad is remote, but it can happen. In most cases, a spark plug will not fail but gradually degrade over time.
Spark plugs are made of durable materials that can withstand high voltage and heat, but they eventually wear out over time. When they start to degrade, there will be warning signs that will lead to reduced engine performance. When this happens, it is time to get a tune-up, which will involve the replacement of the spark plugs.
Usually, most engines have one spark plug per cylinder; however, some more advanced engines have two. This design improves performance and fuel economy but also increases the cost of replacing spark plugs.
Here is a list of the different types of spark plugs:
- Standard copper spark plugs
- Silver spark plugs
- Platinum spark plugs
- Iridium spark plugs
- Ruthenium spark plugs
What are the warning signs of bad spark plugs?
As the spark plugs wear out over time, you may notice some performance issues with your vehicle. Here are a few warning signs that are related to bad spark plugs:
- The vehicle is hard to start
If the spark plugs are worn, the ignition must work harder to generate the spark necessary to ignite the fuel-air mixture in the combustion chamber. Assuming that your battery is good, it is a good bet that the spark plugs are preventing the engine from starting. - The vehicle idle is rough
One sign of a spark plug issue a rough idle condition. Rough idle can be felt from the driver’s seat in the steering wheel or brake/gas pedals. - The vehicle has sluggish acceleration
If the vehicle is slow to pick up speed or does not respond to increased throttle pressure, it may indicate that the spark plugs are not generating an adequate spark. - The vehicle engine misfires
Several issues could cause the engine to misfire, such as leaking valves or poor fuel quality. However, the most common cause is worn spark plugs. The misfires will cause an uncoordinated pace of the engine and possibly loud pops from the engine due to raw, unburned fuel being dumped into the exhaust system. This can become a serious issue as it may impact the catalytic converter. - The vehicle fuel efficiency is reduced
Weak spark plugs will cause the engine to pull more fuel into the combustion chamber to make the vehicle run correctly. This is caused by the spark plugs not effectively burning the fuel-air mixture during combustion. The result will be poor fuel economy.
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What is the cost of changing spark plugs?
Most automakers recommend the replacement of standard spark plugs about every 30,00 to 40,000 miles but if your vehicle has more advanced spark plugs, the interval could increase to as much as 120,000 miles.
The interval is just a rule of thumb, as driving conditions may cause the spark plug to wear out before the recommended service interval. The cost of replacing the spark plugs depends on the type of spark plug and labor charges.
First, let’s take a look at the typical cost of each type of spark plug:
- Standard copper spark plugs are the most common and will range from $2 to $10 each
- Platinum spark plugs are more conductive and will range from $5 to $10 each
- Double Platinum spark plugs use platinum for the center and ground electrodes and range from $10 to $20 each
- Iridium spark plugs provide a more dependable spark and will range from $8 to $30 each
- Double Iridium spark plugs require less energy and range from $8 to $15 each
- Ruthenium spark plugs are longer lasting, burn more efficiently, and range from $15 to $209 each
Now, let’s take a look at labor charges to change spark plugs. The costs here depend on the engine's complexity but, to be more specific, the placement of the spark plugs. The typical engine will allow easy access to the spark plugs in the engine compartment, but in some cases, it may be more difficult to gain access to the spark plugs.
Assuming that the spark plugs are somewhat accessible, you are looking at labor costs from $40 to $350. If you factor in the price of the spark plugs, you are looking at a cost from $100 to $500.
When replacing spark plugs, it is a good idea to replace all of them at the same time to ensure peak performance and avoid issues down the road. It also does not hurt to replace or at least inspect other spark plug-related components, such as the coil pack, spark plug wires, oxygen sensors, and fuel filter, as these components can impact the performance of the spark plugs.
If you are a DIYer, you can use an OBD2 scanner, such as the model 5610 from Innova, to assist you with checking these other components.
Conclusion
Spark plugs play an essential role by providing the tiny lightning bolts needed to burn the fuel in the combustion chamber that turns the engine and moves the vehicle forward. As spark plugs degrade over time, the fuel costs rise, performance drops, and you could run the risk of damaging the catalytic converter, which is a costly component.
You may have given the spark plugs little thought before you read this article, but hopefully, you now better understand how important this small component is. If you are experiencing any of the warning signs, you need to get under the hood if you are a DIYer or take it to a service center and get the vehicle checked out.
Your cost could be as little as $100 or closer to $500, but the piece of mind that you will protect your investment is priceless.
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