How to Know If You Have a Bad Spark Plug?

Brandon Trenton

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Common Symptoms of a Bad or Failing Spark Plug

In order to find the cure or remedy for some disease or solution for a problem, we need to look for the symptoms or signs. This is indeed a natural way of looking for problems.

What is a Spark Plug?

For every new vehicle owner, it is significant to know about different parts of engines and other components of a vehicle. So, a spark plug is a device or tool which is primarily used to deliver the electric current from an ignition system to the combustion chamber of a spark-ignition engine in order to ignite the air mixture by an electric spark.

Importance of Spark Plug

  1. The absence of the spark plug leads to the non-ignition of the fuel or air mixture in the combustion chamber.
  2. The prime purpose of the spark plug is to ignite the air-mixture in the combustion chamber through the passage of an electric signal from the ignition coil.
  3. Considering the key roles of the spark plug, all automobiles necessitate the particular spark plug which is manufactured with specialized material and set by the mechanic during the installation.
  4. The spark plug plays its part when it is of the best quality.

In addition to preceding characteristics, the spark plugs need to be discussed a little more. Just like every other engine part such as fuel filters, motor oil, and so forth, these plugs also require to be upkeep since they might get worn out or stop working.

Need for Replacement of Spark Plugs in Vehicles

A report in the US has demonstrated that the sold automobiles need a replacement of spark plugs after every 30,000 to 50,000 miles. With the advancement in everyday technological sciences, the vehicle designers and manufacturers have so far devised advanced ignition systems that do not need any modifications.

Nevertheless, the manufacturers of products or automobiles will surely guarantee you for its ever-lasting functioning but someday it will really wear out or fail to work properly. In relation to this situation, you need the symptoms of such failures.

6 Common Symptoms of Bad or Failing Spark Plugs

There are six general symptoms for failing spark plugs.

  1. The Slow Acceleration
  2. The Poor Fuel Economy
  3. The Engine is Misfiring
  4. The Engine Surging
  5. The Rough Idle
  6. It becomes difficult to start


1. The Slow Acceleration

The first and noticeable symptom for the bad spark plug is considered to be the slow acceleration. Your vehicle apparently will show no speed when the spark plug is failed. Moreover, these days in new vehicles the sensors are installed just to direct the ignition system when delivering the electric current. In such a situation, the issue may be with the sensor since it might be defective.

Wearing out of the components of the spark plug

Moreover, the second issue that leads to a failed spark plug is the wear out of the components of the spark plug. Since it is made of those tools which operate altogether due to which they are worn out and demonstrate inefficiency in function. This also becomes another reason for slow acceleration and declines in the working condition of the spark plug.

Thus, in case you observe any slow acceleration in your car then you should look for a replacement of your spark plug. At the same time, you need to consult an ASE mechanic to address this issue and find a solution to your problem. The mechanic will also be detailed in relation to this problem and elaborate on the other causes too alongside slow acceleration.

2. The Poor Fuel Economy

The poor fuel economy is another leading symptom of the failure of the spark plug. As we know that a good spark plug assists the fuel to burn effectively in the combustion cycle. When the fuel is burnt efficiently than your vehicle can get better fuel economy.

Space issue between the spark plug rods

In contrast, when the plug does not operate properly then it is normally the issue of the space between the spark plug rods. Space is either too near or too distant. Considering this issue, the ASE mechanic will try to figure out the problem and will modify the spaces as required. Mostly, this happens that they alter the spaces to the factory setting instead of changing it completely.

Hence, when the automobile depicts any increment in the fuel-burning then it is the symptom of spark plug failure.

3. The Engine is Misfiring

The third normal symptom, you will notice is the engine misfiring. It is instantly recognized by every car owner. What does engine misfire mean? It refers to the unsmooth functioning of the car’s engine. Most probably, it is caused by the improper functioning of the spark plug.

The newly aged cars have sensors that demonstrate the signs of malfunctioning but with time the sensors also become faulty which do not show any sign. This malfunctioning is highly considered to be on the grounds of the bad spark plug.

In the same way, the signs of the engine misfire are shown in subsequent ways: increased exhaust emission, poor fuel economy, and reduced engine power. In addition, it also shows sporadic popping sounds from the engine.

4. The Engine Surging or Hesitating

You will eventually notice an engine’s hesitant behavior due to a bad spark plug. This is another worth noting symptom of the failure of the spark plug. This defect indicates that the engine is not reacting well to the driver. It once starts and then shows a sluggish behavior.

The engine starts extracting more air in the combustion

Furthermore, the engine is extracting more air as it should be done in the combustion process. Ultimately, it affects the transmission of power negatively. Consequently, the hesitation and heaving altogether show the bad spark plug issue.

5. The Rough Idle

Has your car felt rough and bouncy when the engine is running? It will obviously feel because of the failure of the spark plug. The automobile gives jumpy buzzes which will further provide a basis for vibrations in your car every next time. Consequently, it can show a spark plug issue when a cylinder goes wrong while being empty.

6. It Becomes Difficult to Start

The last significant apparent sign of failure spark plug is “difficulty of starting”. This symptom shows that the components of spark plugs have worn out.

The reason behind wear out of the parts of the engine is that they operate together and friction cannot be prevented easily. In relation to problems like this, you are required to consult an ASE mechanic just to find a permanent solution for this issue.

However, solutions like a replacement of spark plugs and setting them up at distance also do not endure. At the same, one other thing can help you out in this regard i.e. the upkeep and maintenance of the engine.

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