Foulled Spark Plug: Symptoms and Causes. How to Fix it.

The spark plug is a crucial component of the ignition process for the mixture air-fuel in the combustion chamber. Foul spark plugs can make it more difficult to start the engine as it should. How can you get rid of a fouled sparkplug?

We will be discussing the symptoms and treatment options for fouled sparkplugs in this guide. Also, we will discuss the factors that can lead to this type of failure. We'll also show you next steps. 

What exactly is a Fouled Sparkplug?

The fouled spark plug doesn’t work as a new plug. These plugs become dirty or covered with substances that shouldn’t be on the surface. It is possible to see fuel, carbon or oil in the plug. This can lead to problems with engine performance, fuel economy, and even starting the engine.

Overheating can cause blistering of the fouled spark plug. Foulled spark plugs could cause engine problems or even catalytic converter failure. 

Foulled Spark plugs.

1. The Contaminated Plug

As discussed above, the fouled spark plug isn’t going to look like your new one. The difference would be obvious if the two were placed side by side.

However, most people aren’t pulling the plugs to look at them unless other problems are noticed. Therefore, this probably won’t be the first symptom you come to, but it will be the one that confirms the spark plug is fouled. 

RELATED: 6 Symptoms of Bad Spark Plugs (& Replacement Cost)

2. Hard to Start Engine

The spark plugs will be required to start the engine. If they are fouled, there’s going to be more difficulty cranking the engine over.

The problem might be noticed in small increments. Although it may take a while, the issue will eventually resolve itself if you don't fix it. 

3. Misfiring Engine

When the spark plug can’t help burn the fuel in the combustion chamber properly, misfiring is going to occur. It could begin as a stagger or sputter and then escalate to a more serious problem.

Failing sensors can also lead to these issues. In either case, the Check Engine Light will turn on whenever the engine is misfiring. 

4. Poor Fuel Economy

Whenever the car engine doesn’t operate perfectly, the fuel economy is going to drop. Because fouled spark plugs aren’t burning fuel efficiently, you will end up using more gas.

Poor fuel economy can also be caused by a spark plug gap that’s too far apart or close when compared with factory specifications. You can adjust the gap in this instance. 

5. Reduced response when acceleration is applied

Solid-running engines will react instantly to your touch of the pedal. But, a worn spark plug can cause issues with response. 

Still, trouble accelerating can be caused by numerous factors, so you can’t just assume it’s fouled spark plugs. Instead, you must perform a complete diagnosis to figure out what’s going on. 

6. Rough Idle

Normal operation will result in the engine maintaining a constant RPM. The engine should be able to idle at the same place as it makes a sound.

If the plugs fail, your idle can drop or spike unnecessarily. The ECU may also cause unusual vibrations to try and compensate. 

Related: How to Fix a Car Engine with Rough Idle (10 Causes)

7. Strange exhaust smell

Spark plugs are required to ignite fuel and mixture within the combustion chamber. If the fuel isn’t being ignited properly, it’s going to make its way through the exhaust unburned. 

You may notice gasoline coming out of the vehicle's tailpipe. You may also experience running rich. 

The Causes of Fouled Spark plugs

1. Combustion Chamber Oil Contamination

The main reason for a fouled plug can be oil contamination. Oil contamination can lead to plug failure when oil leaks into the combustion chamber.

It is more common in older cars. However, if your car is burning more oil than usual you may be able to spot the problem quickly. 

READ MORE: Why Is My Car’s Engine Burning Oil? (& How To Fix It)

2. Carbon Buildup

Carbon buildup could cause blackened electrodes or insulator tips of spark plugs. There are many reasons why carbon buildup could occur.

It’s possible that the air filter is dirty, leading to contamination. Altering the rate of combustion could be caused by you driving at a slower speed. You could also experience this if your vehicle is idled too long or the fuel injectors are dirty.

RELATED: 6 Causes of Oil on Spark Plugs (on Threads & in Wells)

3. Overheating Engine

You can overheat the tips of your plugs and cause them prematurely to burn. Overheating may occur due to many reasons but the most common reason is that your cooling system has failed. 

Also, the pre-ignition causes extra heat in your combustion chamber. These situations can lead to engine damage, including premature wear of the spark plug electrode. 

4. Bad Plug Gap

To ensure that the spark can jump, the gap between the plug and the spark must be just right. The calibration of your vehicle will vary. The exact specs can be found in the service manual. However, some spark plugs are pre-gapped.

You should double-check your sparkplug gap setting, even if they are already pre-gapped. If it’s not just right, there will be additional stress on the tip of the spark plug, leading to early erosion. There will be some odd issues with engine performance. 

How to Repair Foulled Spark Plugs

In some cases, cleaning spark plugs can be a smart idea. However, most people find that it’s not worth the time. If you are looking for a cheap solution and don’t mind giving it a try, you won’t be out anything. Of course, the cleaned-up spark plug won’t perform as great as a new one, but it might get you by. 

Follow these steps to clean spark plugs

1. Wipe down the plug and firing tips with a damp rag.
2. You can use a quick drying cleaner such as brake cleaner and fuel injector cleaner. It should be sprayed to the firing side of the plug. Let it rest for at least ten minutes. 
3. Use a wire brush to remove any deposits. 
4. You can use your compressor to remove the spark plug from its firing end. 
5. Check the gap between the spark plugs and make adjustments if needed.

If you don’t clean the spark plug properly, it can fail much sooner. Additionally, you want to figure out what’s causing the plugs to foul and correct that problem or it will just continue. 

In most cases, it’s best to replace the spark plugs once they foul. You can rest assured that your spark plugs are working properly for a minimal price. You can replace the plugs with better ones, which is often faster than cleaning. If your engine is experiencing an issue such as burning oil or other issues, it's important to repair the problem first before plugs become fouled again.

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