Spark Plug Blown: Most Popular Causes and Solutions

Spark plug blown is a phrase that should concern you regardless of whether you are the vehicle owner or driver. Once this happens, it indicates a problem with the plug.

Spark Plug Blown ~ Ran When Parked

In this post, you will learn the popular causes and solutions to blown plugs.

Why Did Your Car’s Spark Plug Blow Out When Driving?

The reason your car had a spark plug blowout while driving is because of cross-threading. This happens when the threads of the spark plugs do not align well with the threads of the cylinder head. Eventually, the pressure in the cylinder can force the plug out of its position.

During combustion, the pressure in the cylinder is significant. It is this pressure that acts on the threads unevenly increasing the likelihood of spark plugs blowout.

Why Car’s Spark Plug Blow Out When Driving ~ Ran When Parked

What’s more, cross-threading can damage the threads of both the cylinder head and the spark plug. The damage interferes with the connection. This decreases the ability of the plug to stay in place.

In addition, cross-threaded plugs are prone to vibrations and stress arising from the engine. This weakens the compromised connection. As a result, it will contribute to the likelihood of seeing a blown-out spark plug.

Using Small Threaded Plugs Can Cause Your Car’s Plug Blowout

Using small threaded spark plugs also known as short-reach spark plugs can cause a blowout. The reason is these plugs’ threads do not extend up their body as high as their long-reach counterparts. This design variation can cause blowouts, especially in engines that favor long-reach spark plugs.

When you use a small threaded plug in an engine that favors a long threaded one, the plug will not have enough thread engagement. This arises from reduced thread contact. As a result, the plugs will be less stable in the cylinder head. This increases the likelihood of the plug dislodging when the engine is running.

In addition, the pressure in the combustion engine demands that plugs withstand it. However, because small threaded plugs have less thread engagement, it compromises their ability to handle extreme pressure. This increases the likelihood of a small threaded plug blowout.

As well, engines operate at a very high temperature which causes materials to expand. When you have a plug that is not secure because of reduced thread engagement, the expansion can create a problem, making the plug loose and vulnerable to a blowout.

Are you wondering – what does a blown spark plug look like? Well, the first thing you will notice is that the plug is unseated from its plug hole in the cylinder head and may show signs of thread damage.

Stripped Cylinder Head Threads: The Hidden Culprit

If your car’s cylinder head threads are stripped, they significantly increase the chances of plug blowouts. The threads keep the plug in place by creating a tight seal.

However, when the threads are stripped, they can prevent the plug from creating a proper seal with the cylinder head. The weak connection makes it easier for the plug to dislodge.

As the pressure builds up during combustion, it creates additional stress making it possible for the loosely connected plug to blow out. As well, the vibrations that your engine generates when running can be amplified by the stripped threads.

The vibrations will make loose the compromised connection between the plug and the cylinder head. Eventually, when one or more of these factors come together, they result in a plug blowout.

Hopefully, this answers your question – why did my spark plug pop out? Probably you are wondering – how far can you drive with a blown out spark plug? The answer is that it is not advisable to drive your car with a blown plug.

Not Tightening the Plug To Optimum Limit Can Cause Blowout

Another cause of plug blowouts is not tightening the plugs to the optimum torque limit. While this weakens the combustion process, it can also result in a blowout because of the irregular distribution of pressure.

A properly secured plug can withstand intense pressure during combustion. However, a loosely tightened one will be unable to withstand the pressure which can result in blowouts.

Furthermore, when the engine is operating, vibrations and movements are inevitable. Therefore, when you have loose plugs, the vibrations will gradually loosen them from their position. With time, the movement increases wear and tear on the threads. This makes it likely for the plugs to be ejected.

As well, your car’s engine generates a lot of heat when running. When you have a plug that is loosely secured, the heat can make it expand and contract at different rates to the head cylinder. The mismatch weakens the connection increasing the risk of a blowout. This explains why a spark plug came out while driving.

Manufacture Flaws Can Cause Plug Blowouts When Driving

Although it is rare, a manufacturing flaw can result in a plug blowout. This defect or error occurs in the production process and appears in the plug’s construction, material, or design. For instance, a plug’s manufacturing flaw can happen if the material has impurities.

Such impurities compromise the plug. Therefore, impurities or inconsistencies in the plug material increase the likelihood of your car’s plug damage and blowouts.

Also, if the process of manufacturing one of the plugs in your car does not meet the precise dimensions, the plug may not fit as it should. It is this lack of proper fit which can result in a loose or uneven connection. This is going to make it vulnerable to vibrations and dislodging when the engine is running.

Moreover, thread imperfections such as irregularities can affect how safely the plug is secured in place. When there are flaws, they can prevent the plug from reaching the necessary torque. This makes them vulnerable to blowouts. In addition, when the assembly process of the various plug components is flawed, it compromises its quality.

A good example is when the alignment of components is off or the welding is insufficient, which compromises the plug’s structural integrity. This weakness becomes apparent when the engine is running since it can cause the plug to fail or blow out.

The common cause of manufacturing flaws is a lapse in quality control during production. A recent manufacturing flaw caused a Ford spark plug blowout recall.

Worn Plugs Increase the Likelihood of Blowouts Nightmare

As your car’s plugs degrade over time, they may compromise the ignition of the air-fuel mixture. When this happens, it increases the likelihood of a blowout. This may happen if your car’s plug ceramic insulation degrades over time. It is this degradation that can cause misfires and electrical leakages that increase the risks of a blowout.

Worn Plugs Increase the Likelihood of Blowouts Nightmare ~ Ran When Parked

Besides, worn plugs force the ignition system to work harder to maintain proper combustion. As a result, the added strain may lead to high energy consumption and overheating increasing the chances of a blowout.

What’s the Solution to the Issue of Blown Spark Plug?

The solution to the issue of a blown plug is to use the right spark plugs. This prevents the issue from happening since the plugs meet the vehicle manufacturer’s specifications. As a result, it decreases issues that lead to plug blowouts.

For instance, using the right plug ensures it fits perfectly in the cylinder head and the combustion chamber. This decreases the likelihood of blowouts happening because of loose connections.

Solution to the Issue of Blown Spark Plug ~ Ran When Parked

Also, when you use the correct plugs, you can apply the recommended torque during installation. This secures the plug in place eliminating chances of blowouts.

As well, using the right plug such as a helicoil spark plug decreases vibrations and movement. This makes them less likely to dislodge when the engine is running because of vibrations. That is one way how to fix a blown out spark plug.

Thread Renewal Can Save Your Engine From Plug Blowout Woes

Another solution is doing a thread repair. Thread renewal helps restore stripped threads in your car’s cylinder head. As such it restores cylinder head thread engagement.

When you do a thread restoration, you restore the integrity of the threads. This allows for a right tightness without the risk of overtightening or insufficient tightening which can cause blowouts.

Doing a thread repair is a cost-effective solution compared to a spark plug cylinder head replacement. That said, you will need a mechanic to use the thread repair kit. It is one way of ensuring the installation is done right.

Purchasing Spark Plugs From Reputable Makers: Top Solution

Buying plugs made by a reputable company can solve this issue. The reason being reputable manufacturers comply with stringent quality standards that ensure their plugs are of high quality.

For instance, plugs from reputable manufacturers are made from materials that provide the necessary durability, conductivity, and heat resistance. This way, they can withstand the extreme stress of the engine.

Moreover, reputable manufacturers make plugs that fit snugly in the cylinder head. Using such plugs decreases the likelihood of loose connections and blowouts. Best of all, they rigorously test the plugs for manufacturing defects that can result in blowouts.

Proper Installation Ensures the Plugs Stay in Place

Another solution is properly installing the spark plugs. With proper installation, you will have to use a torque wrench to tighten the plugs to the recommended manufacturer specifications. This provides normal tightness to make sure the plugs are secure. In turn, you will not damage the threads of the plugs.

When you install the plugs properly, they distribute the pressure evenly across. This reduces the likelihood of a localized stress point eliminating the likelihood of a blowout. In addition, properly installing the plugs avoids cross-threading preventing blowout-inducing leaks.

As well, when you install your car’s plugs correctly, you make sure they are less susceptible to vibrations from the engine. Once you pay attention to the installation process, you will address blowouts before they happen.

Make Spark Plugs Replacement at the Recommended Intervals

You can also solve the issue of blowouts by following the recommended plug replacement intervals by the manufacturer. When you follow the recommended replacement intervals, you ensure the engine gets optimal power. This way you prevent engine misfiring and poor fuel combustion that can result in blowouts.

Also, replacing plugs at the recommended intervals minimizes the risks of wear and tear which can result in a blowout. When you adhere to the recommended plug replacement intervals, you maintain the integrity of your car’s ignition system reducing the risk of a blowout.

Spark Plug Blown Conclusion ~ Ran When Parked


In this post, you have learned the causes and solutions to blown spark plugs. Here are the key takeaways:

  • A blown plug arises as a result of cross-threading, not tightening the plug, or using short-reach plugs.
  • Other causes are stripped cylinder head threads, manufacturing flaws, or worn plugs.
  • To solve the issue, use the right plugs, renew cylinder head threads, or use plugs from reputable makers.
  • You can also solve it by installing the plugs properly and replacing them at the recommended intervals.
  • As well, you can use the services of a professional.

Now, with this understanding, you can diagnose and address the cause of a blown plug.

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