Spark Plug Blew Out of Engine: Why and How to Fix It?

Last Updated on July 20, 2025 by Azim Uddin

If you’re a car owner, you know how frustrating it can be when something goes wrong with your vehicle. One issue that can cause a lot of stress is when a spark plug blows out of the engine. This can happen for a variety of reasons, and the consequences can range from minor to severe.

Reasons why the spark plug blew out of the engine include improper tightening of the spark plug, and overusing the spark plug. Also, constant dirt getting into the engine, improper installation, and defective threads.

Read on as we discuss more about why spark plugs blow out of the engine and ways to fix it properly.

Reasons Why Spark Plug Blew Out of the Engine and Solutions?

Spark Plug Blew Out of Engine

The spark plug blowing out of the engine refers to the sudden expulsion of the spark plug from its designated position in the cylinder head of the engine. This occurrence can happen due to various reasons, such as improper installation or overheating.

Spark plugs blowing out of an engine can be a serious issue. Here are some of the most common causes of a spark plug blowing out of the engine:

If the spark plug is fixed too tightly or is not well tightened to your engine plug, it can cause a spark plug blowout. The result is that the spark plug itself cannot properly channel the electric charge from the plug to the engine block.

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  • Loosen and retighten: If you have overtightened your spark plugs, you can try loosening them and then retightening them to the correct torque setting. However, if you truly over-tightened the spark plug and it got damaged, there’s absolutely nothing you can do about it but to replace it.
  • Use a torque wrench: To prevent over-tightening or under-tightening of the spark plugs, use a torque wrench to tighten the plugs to the factory torque specifications.

Overuse of the spark plug can cause it to wear out and eventually blow out of the engine. Thus, an old or worn-out spark plug leads to issues such as misfiring, poor combustion, and increased stress on the plug and cylinder head.

This potentially makes the plug more susceptible to loosening and blowing out.

  • If your spark plugs are worn out due to overuse, it’s best to replace them with new ones.
  • Use high-quality spark plugs, as this will help to prevent wear and overuse. Also, use spark plugs suitable for the engine and its operating conditions to prevent such issues.
  • Also, regularly check the spark plugs and replace them at the recommended intervals to prevent wear and overuse.
Constant Dirt Getting Into The Engine is a reason of spark plug blew out

Dirt and debris can accumulate in the engine over time, causing the spark plug to become loose and finally blow out.

  • Regularly check the air filter and replace it at the recommended time to prevent dirt from entering your car engine. Also, use a high-quality air filter to keep the engine free from dirt.
  • Clean the engine bay regularly to prevent the accumulation of dirt from entering the engine.
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If the spark plug is installed incorrectly, a blowout will occur. For example, cross-threading during replacement can lead to inadequate threading engagement within the cylinder head. This can cause the plug to loosen and eventually blow out of the engine.

  • Make sure to install the spark plugs correctly and let the engine cool down first. Installing the plugs with a hot engine can cause them to become twisted and misaligned as they cool down.
  • Also, use the best quality spark plugs you can with the correct gap size.
  • Follow the manufacturer’s torque specifications and use a torque wrench to apply the correct amount of force.
  • Avoid cross-threading and use anti-seize lubricant on the spark plug threads to ease future removal.
Spark plug blew out of the engine and stripped the threads in the block.

Threads in the cylinder head can wear out over time due to repeated heating and cooling cycles. If the threads become damaged or stripped, the spark plug may not be able to hold securely, leading to its expulsion.

If the cylinder head threads are damaged, consider using thread repair kits to rethread or install thread inserts. In severe cases, seek professional assistance or consider cylinder head replacement.

Cost of Replacing a Blown Spark Plug

The cost of replacing a spark plug with parts and labor cost inclusive ranges from $100 to $500. Note that the labor cost differs according to engine type. For example, V6 and V8 engines cost more to replace.

car spark plug replacement

FAQs

Below are some frequently asked questions about why spark plugs blow out of the engine and answers to them.

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How often should spark plugs be replaced to prevent blowouts?

It depends on the type of spark plug and the manufacturer’s recommendation. For example, nickel and copper spark plugs should be replaced after they’ve done between 30,000 to 50,000 miles.

Platinum sparks are to be replaced after 60,000 miles. Iridium spark plugs last long and should be replaced after 100,000 – 120,000 miles.

What are the symptoms of a bad spark plug?

Symptoms of a bad spark plug include trouble starting, rough idling, sluggish acceleration, sudden drop, or declining fuel economy. Also, signs like engine misfiring and noise from the engine.

What is the recommended torque for spark plugs?

The recommended torque for spark plugs depends on the cylinder head material, thread diameter, and spark plug type. Most spark plugs are fastened between 8-40 nanometers (nm). Hence, they should be installed according to the torque setting that is recommended by the manufacturers of the spark plug.

The recommended torque for M12 spark plugs is 15-20N・m, which is about 1/3 turn and about 1/12 turn. It is important to use a torque wrench to avoid over or under-tightening the spark plugs

Conclusion

A spark plug blowing out of an engine is a serious issue that can lead to potential damage to your engine and poses safety risks, too. It requires immediate attention and repair. Hence, there are several reasons why it can happen. Improper tightening, improper installation, etc, are some of the most common causes of a spark plug blowing out of the engine.