Signs of broken spark plugs, how to check and replace them

When the spark plug is broken, it will greatly affect the car engine, not only making it difficult for the car to start and consuming fuel, but the car will also jerk and lose power.

Bugi’s main mission

caron pro car spark plugs

Spark plugs are an important component in the car’s ignition system. The main task of the spark plug is to create an electric fire in the combustion chamber to ignite the fuel-air mixture in the cylinder. This helps the engine operate efficiently and stably. However, like any other component, spark plugs can also experience damage and need to be checked and replaced at the right time.

Structure of Spark Plug

caron car spark plug structure

Includes the following main sections

Spark Plug tip (Spark Plug tip)

This is the part of the Spark Plug that is in direct contact with the combustion space in the engine’s combustion chamber. It has a positive electrode and a negative electrode separated by an insulating gap.

Center electrode

This is the electrode placed in the middle and is the point where the flame is created. It is made from high heat resistant materials such as corrosion resistant steel alloys.

Ground electrode

The negative electrode is a ring or small rods placed around the positive electrode. It has the function of conducting electricity and creating an electric field to burn fuel.

Spark Plug Gap

This is the space between the negative electrode and the positive electrode, kept apart by an insulating layer. The size of the insulator gap is important for the production of a strong and stable flame.

Insulation layer (Insulator)

The insulating layer surrounds the positive electrode and between the two electrodes. Plays an insulating role to prevent electric flames from spreading beyond the spark plug tip and ensures that only electric flames create an insulating gap.

Spark Plug Shell (Shell)

The spark plug shell is the outer covering of the spark plug and has the function of protecting the internal components from the outside environment

The main structure of the spark plug is designed to withstand high temperatures, pressures and voltages. Spark plugs are responsible for creating a strong electric fire to ensure complete combustion of the fuel-air mixture and maintain stable performance of the car engine.

Principle of operation of spark plugs

The combustion process includes three components: fuel, oxygen and heat. With each charging cycle in a car engine, the cylinder will absorb about 21% of oxygen. If it is a multi-point injection engine, the fuel will be injected immediately during the intake cycle. For direct injection engines, fuel will be injected during the compression cycle.

Heat is supplied in the form of small lightning bolts in the gasoline engine. High voltage will be generated in the ignition wire and the engine control module (ECM) will control this process. The electrical charge will be transmitted through the connecting wire to the spark plug. A spark will occur if the charge jumps between the two electrodes within the range of 0.25 mm to 1.8 mm. Progress spark plug This will generate temperatures from 4,700 °C to 6,500 °C to burn the previously compressed fuel and air mixture and push the piston down in the compression cycle.

Classification of Spark Plugs

Standard Spark Plug

This is the most common and popular type of spark plug. Original spark plugs are designed to meet the general requirements of the engine and can operate well under normal conditions. It is suitable for cars with no special requirements and is used for many different car models.

Double Platinum Spark Plug:

This type of spark plug has a layer of silver or platinum covering both the positive and negative electrodes. Silver or platinum coating provides corrosion resistance and extends the life of the spark plug. Dual spark plugs are often used in ignition systems that require high stability and durability.

Iridium Spark Plug

Iridium spark plugs have positive electrodes made from iridium, a rare and highly durable metal. This material helps enhance corrosion resistance and prolong the life of spark plugs. Iridium spark plugs are often used in high-performance engines and require precise ignition.

Platinum Spark Plug

Platinum spark plugs have a positive electrode or both electrodes made from platinum. Platinum is more resistant to corrosion than other metals, and also helps create a stable and reliable electric flame. Platinum spark plugs are suitable for medium performance engines and are popular in the automotive industry.

Silver surface spark plug

Silver Spark Plug: This type of spark plug has a positive electrode or both electrodes coated with silver. The silver coating enhances electrical transmission and improves ignition performance. Silver surface spark plugs are often used in applications that require fast ignition speeds and high sensitivity.

How many kilometers should I go to replace the spark plug?

When to change spark plugs depends on many factors such as engine type, manufacturer and type of spark plugs used. However, there are some general instructions for replacing spark plugs as follows

– Consult the manufacturer: See the vehicle manufacturer’s manual or the spark plug manufacturer’s instructions to see how often they recommend changing spark plugs for your vehicle.

– Spark plug replacement interval: Normally. Spark plugs need to be changed when traveling 20,000 – 30,000km

– Check spark plug condition: Check the spark plug condition periodically to ensure they are working well. If the spark plug shows signs of damage such as low water, severe wear or loss of electrodes, the spark plug should be replaced immediately, even if the normal spark plug replacement mileage has not been reached.

– Operating conditions: If you frequently operate in harsh conditions such as congested traffic conditions, driving at high speeds or operating in dusty environments, you should consider replacing your spark plugs sooner to ensure ensure good performance.

– Check spark plugs periodically: If the spark plug is seriously corroded, rubbed or shows signs of damage, you should replace it immediately.

Signs that the Spark Plug is weak or has a problem

Difficulty starting the car

A common sign of a bad spark plug is difficulty starting the vehicle. When the spark plug is not working properly, it does not produce enough electrical flame to burn the fuel. As a result, you may have difficulty starting your vehicle, especially in cold weather. You may feel intermittent or the engine not starting immediately when you turn the ignition key.

The engine operates unstable

Damaged spark plugs can cause unstable engine operation. You may feel vibrations, jerking or loss of power while driving. This usually happens when the spark plug does not produce a strong enough electrical flame to ignite the fuel-air mixture. When the engine is not running smoothly and responding well, spark plugs can be a potential cause.

The car is wasting fuel

A bad spark plug can lead to a significant increase in fuel consumption. When spark plugs aren’t working properly, there isn’t enough electrical flame to burn the fuel effectively. As a result, the engine needs to use more fuel to maintain performance. If you see an increase in fuel consumption for no other obvious reason, spark plugs may be the cause.

Abnormal spark plug color

The color of the spark plug can also provide information about its condition. Under normal conditions, new spark plugs or spark plugs in good condition are usually light brown or gray in color. However, a damaged spark plug may appear oily black or have black patches, indicating that the fuel is not completely burned and there is a buildup of residue. Spark plugs may also be white or have white patches, indicating that the spark plug is overheating and not working effectively.

Weak engine

When the driver steps on the accelerator to accelerate the vehicle, the ECM will control the spark plug to create strong sparks to burn more fuel and produce more power. However, if the spark plug is weak, damaged, defective, etc., the electron beam may not be strong enough. This causes the movement to be weaker than normal.

The Check Engine light is on

Caron engine warning light

When the Check Engine light comes on, it means the engine is having problems. When the engine or some related parts have any problems, the Check light will light up to notify the driver. If you see the Check Engine light flashing, it is likely that the car’s spark plugs are having problems.

Signs of broken spark plug

The best way to identify broken car spark plugs is to directly check the spark plug condition. When removing the spark plug for inspection, use a clean soft cloth to clean the area around the spark plug base. Use dry spray to clean all the soot accumulated in the spark plug pot. Don’t forget to soak the spoke tip in gasoline. Absolutely do not chip or break the porcelain insulator.

Observing the color and size of the spark plug gap is a way to determine whether a car’s spark plugs are broken or not. Through this you can accurately assess the condition of your car’s spark plugs.

Large spark plug gap distance: This is a sign that the spark plug is very worn. Because the more worn the spark plug is, the larger the spark plug gap will be. The allowable spark plug gap distance is only about 7 – 12 mm. If this limit is exceeded, it means the spark plug is worn out and needs to be replaced.

The spark plug negative pole is worn, the corners are rounded: A worn cathode, most notably the rounded corners, is a sign that the spark plug is heavily worn and needs to be replaced. The new spark plug’s cathode is very square and the corners are sharper for better ignition. The more worn the cathode is and the more rounded the corners are, the worse the ignition will be.

The spark plug ceramic cover is broken: A broken spark plug ceramic cover can be caused by force due to improper installation.

Rusted spark plugs: Rusted spark plugs can be caused by deposits that have not been cleaned for a long time. Rusty spark plugs will easily lose their ability to ignite and cause delayed ignition, reducing engine power.

Spark plug leaks: A melted spark plug is a sign that the spark plug is damaged and needs to be replaced. In addition, this is also a sign that the car engine is having problems such as poor quality gasoline, malfunctioning ignition coils…

Spark plug replacement price

The price of replacing Spark Plugs can vary depending on many factors such as: Type of Spark Plug, brand, vehicle type, repair place.

But usually, there is not much difference in price, ranging from 800,000 – 1,500,000 million VND/set of 4 spark plugs.

Reputable place to replace spark plugs


CarOn Pro – 5S standard car service system

Caron Pro is trusted and known by customers as a chain of 5S standard auto repair service centers. With extremely modern equipment, genuine spare parts, skilled technicians, a full range of services at extremely affordable prices and quality.

Please contact us immediately via Hotline: 0961.247.360

Facility 1 – CarOn Xuan Phuong
Lot P3, Thi Cam Street, Xuan Phuong, Nam Tu Liem, Hanoi
Phone: 0919009069
Facility 2 – CarOn Hoang Quoc Viet
455 Hoang Quoc Viet, Co Nhue 1, Bac Tu Liem, Hanoi
Phone: 1900633612
Facility 3 – CarOn Lai Xa
Km14, National Highway 32, Lai Xa, Kim Chung, Hoai Duc, Hanoi (next to Hoai Duc welcome gate)
Phone: 0384653472
Facility 4 – CarOn Care Phap Van
No. 4 – BT5 Phap Van Urban Area, Tran Thu Do Street, Hoang Mai, Hanoi
Phone: 0985333589
Facility 5 – CarOn Care Thai Nguyen
76 Viet Bac Street, Dong Quang, Thai Nguyen
Phone: 0975782639
Facility 6 – CarOn Care An Khanh
Bao Son Paradise Villa Area, Hoai Duc, Hanoi
Phone: 0963598600

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