Table of Contents

Key Takeaways

The following are the key takeaways from this article:

  • Internal combustion engines have sparkplugs for each cylinder.
  • The function of the sparkplug is to produce a voltage spark to ignite the air-fuel mixture inside the combustion chamber.
  • The sparkplugs can go faulty due to overheating, deposition of carbon, and oil in the combustion chamber.
  • Faulty sparkplugs will result in trouble starting the car, idling the engine, and poor fuel economy.
  • The cost to resolve sparkplug issues can range between $16-300.

Introduction

Internal combustion engines combust the fuel to produce mechanical energy. When the piston compresses the fuel in the combustion chamber, the sparkplug becomes the most important part (1). The sparkplug stores voltage inside it from the distributors and ignite the air-fuel mixture for combustion.

If a sparkplug is worn out, it will not emit a spark, and the particular engine cylinder will misfire. So, checking sparkplugs and replacing them after covering particular mileage is recommended.
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This article will further analyze the function, common problems, and symptoms of bad sparkplugs.

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The function of Sparkplugs

Sparkplugs are one of the most important parts of the engine and play a vital role in igniting a spark in the combustion chamber. The spark produced by the sparkplugs is responsible for igniting the air and fuel mixture in the combustion chamber.

Sparkplugs are situated at the top of the cylinder head and attached to the combustion chamber’s ignition coil. This helps produce the right voltages required to initiate the combustion phenomenon.
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To maintain the engine’s health, it is necessary to ensure the health of the sparkplugs and the electrodes.

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Car vacuum cleaners come in many designs and forms, the most common of which is the handheld car vacuum. Top 15 Best Car Vacuum Cleaners in 2018 cleaner.
Damaged sparkplugs can cause serious damage to the engine system. Furthermore, the other function of the sparkplug is to remove the excessive heat from the combustion chamber.

Sparkplugs are heat exchangers that remove all the excessive heat by transferring it to the engine’s cooling system. The sparkplugs are usually made up of silver, platinum, and steel. Steel is less durable, so the mostly sparkplugs are made of steel and platinum because they have durable life (2). The sparkplugs play a vital role in accelerating the vehicle. Therefore, it is important to maintain the functioning of sparkplugs. Otherwise, the engine can face serious issues such as less power generation, engine misfires, etc.

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Common Problems with the Sparkplug

Overheating of Sparkplug

Sparkplugs are important components of the engine and and their role is to ignite the fuel in the combustion chamber. Therefore if they’re damaged, they can significantly impact the engine’s overall performance and function.

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The major reason for the failure of the sparkplug is overheating. Excessive overheating can lead to the failure of the sparkplug. This overheating can occur for various reasons, such as the excessive burning of fuel in the combustion chamber and the defective cooling system.

The pre-ignition of the spark is one of the major reasons for producing a large amount of heat in the combustion chamber, which affects the spark plug. Also, the defective cooling system is considered a major reason for the failure of the sparkplugs, as excessive heat will accumulate in the engine (1). Thus, the electrodes of the sparkplug will get damaged when the temperature reaches above 800 °C. As a result, the sparkplug will become red, resulting in abnormal engine combustion. As a reaction, the engine’s performance will get damaged, and there are chances that there will be less acceleration in the vehicle and vibration will be produced in the engine due to poor ignition phenomenon (4).

Oil in Combustion Chamber

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The other major reason for the failure of the sparkplug is the presence of oil in the combustion chamber. Sometimes, the engine oil enters the combustion chamber, making the sparkplug oily and dirty.

The dirt and debris in the oil will lead to the failure of the sparkplug. The engine oil can enter the sparkplugs due to various factors, such as damaged valve cover gaskets, broken piston guide, and defective spark O rings (2). Thus, it results in the poor performance of the engine. Due to the oily sparkplugs, there are chances that bluish-black smoke will be released from the tail pipe. This happens because the oily sparkplugs start consuming more fuel, and the fuel is not burnt properly, which results in the release of bluish-black colored smoke. This happens because the opening and closing of the valves do not occur due to the failure of the sparkplugs, and the amount of air and fuel is disturbed in the combustion chamber (3). Moreover, the fuel economy gets disturbed due to the broken sparkplug, and a slight increase in fuel consumption is observed. This excessive fuel burning will create an oxidized coating on the tip of the sparkplugs, and the powerful spark is not produced as a response.

Deposition of Carbon Sparkplugs

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The other major reason for the sparkplugs’ failure is the deposition of the carbon layer on the sparkplugs’ electrodes. This problem usually occurs when the air filter is damaged and letting dirty air enters the chamber.

Also, the disturbing ratio of air and fuel in the combustion chamber results in the deposition of black soot on the electrodes. As a result, the performance of the sparkplug becomes effective. Due to this issue, there are chances of the engine misfire. Engine misfire usually occurs when there is declined combustion phenomenon. Thus, it will create troubles for the accelerator, and the electrode will produce a strong spark leading to an engine misfire. Besides, engine backfires also occur due to damage to sparkplugs. This happens when the fuel is not completely burnt and is left through exhaust valves (3). During this process, mini-explosions damage the engine’s performance.

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Symptoms of a Bad Sparkplug

Following are a few symptoms of a bad sparkplug:

Trouble Starting the Car

The most common symptom of a bad sparkplug is trouble starting the car. Usually, when the car does not start, low battery is thought to be the primary reason behind it.

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A clogged or burnt sparkplug will also cause trouble starting the car. Sometimes, the car will take longer to start, and sometimes, the car will not.

In this case, it is recommended to replace the sparkplugs and try starting the car (5). Of course, you can always order sparkplugs at online platforms, but do ensure the sparkplug specifications to avoid wrong orders.

Idling Engine

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Rattling and knocking sounds might be the symptom of a bad sparkplug. These sounds indicate that the engine is idling and some components are malfunctioning.

Usually, an idling engine is caused by the malfunctioning crankshaft, cams, etc. In rare cases, a faulty sparkplug will also cause an idling engine (5). It is recommended to schedule an appointment with a professional when you experience an idling engine to avoid permanent engine damage.

Poor Fuel Economy

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When sparkplugs have gone bad, they cannot burn the fuel efficiency in the combustion chamber.

The car will need more fuel to produce the desired engine power. If a car owner is experiencing a sudden drop in fuel economy, then there is a chance that the sparkplug of a particular cylinder has gone bad (1). In this case, you must replace the sparkplugs before driving long distances.

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Cost to Resolve Sparkplug Issues

Common Sparkplug IssuesCost to Resolve the Issue
Bad Sparkplug$16-50 to replace the bad sparkplug set
Faulty Sparkplug Coil$200-300 to replace faulty sparkplug coil
Bad Sparkplug Hole$100-200 to replace the sparkplug hole issues

Conclusion

To conclude, a sparkplug is an essential component in the combustion process. This part ignites the air-fuel mixture through the voltage spark that other kicks in the combustion process. But, first, you must ensure that the sparkplugs are performing effectively to avoid trouble starting the car, idling the engine, and poor fuel economy.

FAQs

It depends upon the model of the vehicle. You are recommended to replace the sparkplugs every 30,000 miles. For further information, you can consult the instruction manual of your vehicle. Similarly, if the sparkplug has gone faulty before this mileage, you should replace them immediately to avoid further issues.

The common symptoms of bad sparkplugs include trouble starting the vehicle, idling the engine, poor fuel economy, rattling engine sounds, etc. In some cases, the car might not start as well, indicating that the sparkplug has gone bad and is not producing a spark that ignites the air-fuel mixture to start the vehicle.

You should replace the faulty sparkplugs earliest to avoid further engine complications. However, you can drive for small distances with bad sparkplugs.

References

About Author

Andrew Ray

Andrew is an automotive technician with 10 years of experience mainly in American and Japanese cars, covering everything from routine vehicle maintenance and engine inspections to tire rotation.