7 Symptoms of a Fouled Spark Plug that You Must Know

When spark plugs aren’t functioning properly they result in rough idle, poor fuel efficiency, a lack of power, and even check engine lights indications. Spark plugs are an essential component to the smooth operation of any gasoline-powered internal combustion engine.

It is the role of the spark plug to ignite the fuel that is contained inside the combustion chamber. An electrical signal is sent to the ignition coil from the engine control unit, also known as the ECU. The 12 volts that are supplied to the ignition coil are amplified to several thousand volts. This increased voltage generates a “spark” in the space between the spark plug electrodes, which ignites the air-fuel combination.

In this article, we will be discussing the most common symptoms of a fouled spark plug. Let’s get started.

What is the Typical Lifespan of a Spark Plug?

The lifespan of spark plugs is highly dependent on the specific use. In comparison to plugs in automobiles, motorbike plugs have a shorter lifetime. This is because the RPMs seen by a motorbike engine is much greater.

Motorbikes often rotate at speeds of 8,000 or more revolutions per minute (rpm) causing the spark plug to ignite an average of 2,000 times per minute. Whereas an automobile will typically function between 2,000 and 3,000 revolutions per minute, which results in between 500 and 750 spark plug ignitions each minute.

The materials that are utilized to make spark plugs may have a significant impact on their lifespan. Copper plugs can last for between 10,000 and 20,000 miles, whereas platinum or iridium plugs may last for 60,000 miles or more. Copper plugs are the least expensive option.

Spark plugs in automobiles and trucks may last anywhere from 30,000 to even 100,000 miles, however the plugs in motorbikes only have a lifespan of 15,000 miles on average.

 The intervals between replacements might fluctuate by as much as 70,000 kilometers depending on the application.

 7 Signs of a Defective Spark Plug

Idling roughly, poor acceleration, decreased fuel efficiency, misfiring, difficulty in starting, and even the dreaded check engine light are typical indications that the spark plugs need to be replaced. The wide range of problems that may be brought on by spark plugs that aren’t working properly demonstrates how essential these components are to your vehicle’s engine.

 The following are seven common symptoms of a fouled spark plug:

1. The Warning Light for The Engine

A check engine light may be activated if the spark plugs in the engine are faulty. In more extreme instances, it may cause the check engine light to begin blinking.

 When the check engine light is on, a specific code will be triggered. Check out this code and see if you can figure out what it stands for. A cylinder misfire is indicated by the P0300 code, which may be connected to the spark plugs. In contrast, a P0171 code shows that there is a problem with the PCV valve.

2. Black Exhaust Smoke

Defective spark plugs may also be the cause of exhaust smoke that is thick and black. If you see this indication of a malfunctioning spark plug, it is highly recommended that you take your vehicle to a professional auto repair shop or a qualified technician as soon as possible.

 It is quite probable that the issue is multi-faceted (may be an issue with the CAT).

3. The Engine Has a Misfire

Misfires in the engine have the potential to set off the check engine light, although this is not always the case. There are occasions when the engine may misfire but your dashboard will not give you any warning. When this occurs, you may experience more vibration, with the possibility that the vibration will go away as the speed increases.

A misfire occurs when the spark plug in the combustion chamber is unable to ignite the combination of air and fuel that is present in the chamber. When anything like this takes place, the forces inside the engine become imbalanced, which in turn causes vibration.

4. Idle Roughness

Spark plugs that are not working properly might be the cause of an engine that idles roughly. What ends up happening is that the spark plug fails to ignite the gasoline that is present in the cylinder, which results in an abnormally high amount of fuel being expelled from the engine via the exhaust. While this occurs, the O2 sensor is misled into believing that the engine is receiving an excessive quantity of gasoline when, in reality, the engine is receiving the correct amount of fuel.

 After this, the erroneous data is passed to the ECU, and the ECU makes the necessary adjustments to create a proper air-fuel combination. When this happens, the engine has a difficult time running the low mixture, which is what leads to a rough idle.

5. Reduced MPGs

There is a strong correlation between several of these symptoms. If you find that your engine is misfiring, you will probably also notice that your vehicle is getting a reduced mileage. This occurs when the gasoline in the cylinder is not properly ignited throughout each cycle of the combustion process by your engine.

The gasoline that is squandered is expelled via the exhaust, which results in a decrease in fuel efficiency.

6. Slow acceleration

If your spark plugs are worn out and not firing properly, one of the symptoms that you could see is a slow acceleration rate. If you have a larger engine with eight cylinders, you’ll only have seven of them working (and a lot of vibration), but if you have a more compact engine with four cylinders, you’ll only have three of them working.

This decrease in the number of cylinders results in a loss of power and, as a direct result, a drop in acceleration. If your engine has a V configuration (v6, v8, etc.), you will likely feel greater vibration than if it had an inline arrangement with just four cylinders. This is due to the fact that an engine with all of its cylinders lined up in one line would experience less of a shift in balance in the event of a misfire.

7. Difficulty in Starting

The fact that the engine is difficult to start is the last indication that the spark plugs are not functioning properly.

It may take a great deal of effort to spark the plugs and get the gasoline to ignite if the plugs are old and worn or if they are unclean. Because the engine is cold, it is more difficult to start than it would be if it had reached its normal working temperature.

The Bottom Line

Spark plugs are an integral part of how an engine functions. They are capable of causing a wide variety of issues, yet many times those issues are intertwined with one another.

When it comes to the recommended intervals for replacing spark plugs, always be sure to follow the instructions in the manufacturers handbook. Depending on the material used for the spark plugs, the intervals between spark plug replacements might vary anywhere from 15,000 to 100,000 miles.