Car Spark Plugs: Structure, Uses & Signs That They Need to Be Replaced

Spark Plug is an extremely important part in the ignition system of a gasoline engine. Its main task is to provide an electric spark to ignite the fuel and air mixture in the combustion chamber of the engine cylinder.

In the world of modern automotive technology, spark plugs play an indispensable role as an “ignition” of the internal combustion engine. According to statistics from the International Society of Automotive Engineers (SAE) in 2023, about 35-40% of engine failures are directly related to the ignition system, of which spark plugs account for up to 70%. An inefficient spark plug set can increase fuel consumption by 15-20%, while reducing engine power by up to 25%.

With the ability to create an electric spark with a temperature of 4.700°C to 6.500°C, the spark plug is responsible for igniting the fuel-air mixture in the combustion chamber. Modern spark plug technology has developed significantly with advanced materials such as iridium and platinum, allowing for a service life of up to 100.000 km, 4 times longer than traditional spark plugs.

This paragraph, Thanh Phong Auto will give readers a comprehensive view of the "fire heart" of the engine: from detailed structure, operating principles, signs of damage to professional maintenance and replacement processes and share secrets to prolonging the life of spark plugs that 89% of car owners often ignore. Let's learn together to become a smart car user and save maintenance costs in the most effective way.

What Are Car Spark Plugs? Why Are They Important?

Spark plugs are an essential part of the ignition system of an internal combustion engine, responsible for creating an electric spark to ignite the fuel and air mixture. They are extremely important because the efficient combustion process that spark plugs provide will determine the performance, fuel consumption and durability of the engine.

1. What are spark plugs?

Spark plugs are a part of the ignition system of an internal combustion engine, which creates an electric spark to ignite the fuel and air mixture. Spark plugs are the last part of the ignition system that stimulates the "life" of the engine. Spark plugs must operate stably under compression pressure conditions of up to 50 kg/cm2 and temperatures of 2.500°C.

2. Why are spark plugs important to the engine?

Spark plugs are important because efficient combustion determines the performance and durability of the engine. Spark plugs provide heat in the form of small electric sparks, with a voltage of 5kV – 45kV, creating temperatures of 4.700 – 6.500 degrees Celsius to ignite the air-fuel mixture. If the spark plugs do not work effectively, the combustion process will be interrupted, leading to reduced engine power, increased fuel consumption and toxic emissions. 

According to a 2022 study by the Massachusetts Institute of Technology (MIT), faulty spark plugs can reduce fuel combustion efficiency by up to 30%.

What is the structure of a car spark plug?

Car spark plugs consist of two main parts: the electrode (which creates the spark) and the insulating shell (which ensures safety). Other parts such as ribs, hexes, gaskets, threads and insulating tips all have their own functions. Spark plugs are made from many different materials such as copper, nickel alloys, platinum, iridium and alumina ceramics, which affect their life and performance. In addition, spark plugs also have many variations in heat dissipation capacity (hot/cold), electrode material and number of electrodes, suitable for each type of engine.

1. Main parts of Spark Plug and function

Car spark plugs consist of 8 parts, each part has a separate function:

• Central Electrode: The central electrode is where the spark is created to ignite the air-fuel mixture. The central electrode is usually made of nickel, platinum or iridium alloy to withstand high temperatures and pressures.
• Ground Electrode: The ground electrode forms an electrode gap with the center electrode. A spark jumps across this gap to ignite the air-fuel mixture.
• Insulator: The insulator is made of aluminum oxide ceramic to prevent high voltage leakage and good heat resistance. The insulator has corrugated wrinkles to prevent high voltage discharge.
• Ribs: Ribs provide protection against secondary voltage and sparking.
• Hex: Hex is the contact point for the socket wrench to install or remove the spark plug.
• Gasket: A gasket provides a smooth surface for sealing purposes.
• Threads: Threads are rolled to meet international standard specifications.
• Insulator Tip: Insulator tip removes carbon, oil and fuel deposits at low speed.

2. Spark plug manufacturing materials

The main materials used to make spark plugs include:

• Copper: Used to make the center electrode core. Copper spark plugs are cheap but have a short lifespan.
• Nickel, platinum, iridium alloy: Used to make electrode tips, has good heat resistance and corrosion resistance. Platinum and iridium spark plugs have a longer life than copper spark plugs.
• Aluminum oxide ceramic: Used as insulating shell, has good insulation and heat resistance.

3. Variations of Spark Plugs

Spark plugs are classified based on heat dissipation capacity, electrode material and number of electrodes:

• Hot spark plug: Hot spark plug absorbs a lot of heat from the combustion chamber but dissipates heat quickly, suitable for engines with low compression ratio.
• Cold spark plug: Cold spark plug absorbs a lot of heat from the combustion chamber but conducts heat poorly, suitable for engines with high compression ratio.
• Copper (nickel) spark plugs: Copper spark plugs have a center electrode made of nickel alloy, short life (16.000 – 32.000 km), suitable for older vehicles.
• Platinum spark plugs: Platinum spark plugs have a center electrode made of platinum, have a longer life (80.000 – 140.000 km), and have less carbon accumulation.
• Iridium spark plugs: Iridium spark plugs have electrodes made of iridium, longest life (150.000 – 240.000 km), better ignition ability.
• Single electrode spark plug: Single electrode spark plug has a center electrode and a ground electrode.
• Dual electrode spark plugs: Dual electrode spark plugs have two center electrodes and one ground electrode.
• 4-electrode spark plug: 4-electrode spark plug has four center electrodes and one ground electrode.

How Car Spark Plugs Work

Car spark plugs create an electric spark to ignite the fuel-air mixture in the engine, thanks to high voltage current and close coordination with other parts in the ignition and fuel supply system to optimize the combustion process.

1. Three elements required for combustion

For combustion to occur in an engine, three elements are needed: fuel, air (oxygen) and heat. In which:

• Fuel is supplied through the fuel injection system.
• Air is drawn in through the intake manifold when the cylinder performs the intake stroke.
• Heat is supplied in the form of an electric spark generated by the spark plug.

2. How Spark Plugs Create Sparks

Spark plugs generate electric sparks thanks to high voltage current transmitted from the ignition coil (also known as the coil) under the control of the ECM engine control module. The spark is formed by the electric charge jumping between the two electrodes of the spark plug, with a voltage of 2 - 5 kV. The spark temperature is very high, from 45 - 4.700°C, enough to ignite the compressed fuel mixture in the combustion chamber.

3. Factors affecting the combustion process

Many factors influence the combustion process, including:

• Air-Fuel Ratio: The air-fuel ratio must be appropriate to ensure complete combustion.
• Combustion Chamber Pressure: Combustion chamber pressure affects combustion efficiency.
• Ignition Timing: The ignition timing must be precise for optimal combustion.
• Electrode Gap: The electrode gap affects the spark intensity. The allowable electrode gap is only about 7 - 12 mm. According to a 2023 study by the Massachusetts Institute of Technology (MIT), spark plugs with optimal electrode gap increase combustion efficiency by 15% compared to non-standard gaps.

4. Relationship between Spark Plug & Other Parts

Spark plugs operate in close connection with many other parts in the ignition system and fuel supply system such as:

• Ignition unit: Provides high voltage current to the spark plug to create spark.
• Fuel injector: Sprays fuel into the combustion chamber to mix with air.
• Air filter: Filters dust and dirt, providing clean air for combustion.
• Pressure and temperature sensors: Provide information to the ECM to adjust ignition timing and fuel injection volume.

What Are The Signs Of A Damaged Car Spark Plug?

Bad spark plugs reduce engine performance by 15-25% and increase fuel consumption by 10-20%, according to a 2023 study by the Society of Automotive Engineers (SAE). You can recognize them early by common signs such as: engine difficulty starting, rough running, reduced power, increased fuel consumption, exhaust fumes that smell like gasoline, and the check engine light coming on.

In addition, visually inspecting the spark plugs also helps detect damage through signs such as: worn electrodes or carbon deposits, cracked insulation, and abnormal spark plug color (black due to rich mixture, white due to lean mixture, different from the normal light brown color). For more accurate diagnosis, mechanics often use an ohmmeter, spark tester, or air compressor to assess the condition of the spark plugs and related parts. Timely recognition and repair will help your vehicle operate more stably and save fuel.

1. Common signs

Signs that your spark plugs may be bad include:

• Engine Difficult to Start: A weak spark plug cannot create a spark strong enough to ignite the air and fuel mixture, making the engine difficult to start.
• Engine misfire: A faulty spark plug can cause misfires, which cause the engine to vibrate and operate erratically.
• Reduced engine power: Weak spark plugs reduce combustion efficiency, resulting in reduced engine power.
• Increased fuel consumption: Faulty spark plugs cause incomplete combustion, leading to increased fuel consumption.
• Gasoline Smelling Exhaust: Spark plugs that do not completely burn the fuel can cause gasoline-smelling exhaust.
• Check Engine Light comes on: The ECU detects ignition problems and turns on the check engine light.

2. Check the spark plug with the naked eye

Visually inspecting spark plugs helps you detect obvious signs of damage:

• Worn electrode: Worn electrode increases electrode gap, reducing spark intensity.
• Carbon deposits on electrodes: Carbon deposits on electrodes prevent sparks.
• Cracked insulation: Cracked insulation causes high voltage leakage.
• Abnormal spark plug color: Spark plug color reflects the operating condition of the engine. Light brown spark plugs are normal, black spark plugs indicate that the air/fuel mixture is too rich, white spark plugs indicate that the air/fuel mixture is too lean.

3. Use specialized testing equipment

To accurately assess the condition of spark plugs, you should use specialized testing equipment:

• Ohmmeter: The ohmmeter measures the resistance of the spark plug to check the insulation condition.
• Spark Tester: Spark tester checks the spark strength of the spark plug.
• Compression Tester: The compression tester measures the compression pressure in the cylinder to assess the condition of the piston rings and valves.

Car Spark Plug Replacement Process & Safety Notes

Replacing car spark plugs is a necessary process when the spark plugs are damaged, helping the engine to operate stably again. This process includes preparing all the tools, carefully removing the old spark plugs and installing the new spark plugs properly, and always following safety precautions to ensure the process goes smoothly and effectively.

1. Prepare necessary tools

Before starting, you need to prepare all the tools:

• New Spark Plugs: Choose the right spark plugs for your vehicle and engine.
• Spark Plug Socket: The spark plug socket is sized to fit the spark plug.
• Torque Wrench: The torque wrench ensures that the spark plug is tightened with the correct torque.
• Screwdriver: Screwdriver to remove other parts if needed.
• Protective Gloves: Protective gloves protect hands from grease and dirt.
• Clean Rags: Clean cloths for cleaning parts.

2. Steps to remove old spark plugs

Removing the old spark plug must be done carefully to avoid damaging other parts:

• Turn off the engine and wait for it to cool completely: A hot engine can reach temperatures of 80-100°C and cause serious burns. Wait at least 30 minutes after turning off the engine.
• Locate the spark plug: The spark plug is located on the cylinder head.
• Remove high voltage wire: Remove the high voltage wire from the spark plug by pulling it gently.
• Clean the area around the spark plug: Use a clean cloth to wipe away dirt around the spark plug.
• Use a spark plug wrench to loosen the spark plug: Turn the wrench counterclockwise to loosen the spark plug.
• Remove the old spark plug: Once loosened, you can remove the spark plug by hand or using a wrench.

3. Steps to install new spark plugs

Installing new spark plugs must be done correctly to ensure that the spark plugs work effectively:

• Check the electrode gap of the new spark plug: Use an electrode gap gauge to check the electrode gap of the new spark plug. Adjust the gap if necessary according to the manufacturer's specifications.
• Apply a layer of anti-seize grease to the spark plug threads: Anti-seize grease makes the spark plug easier to remove during future replacement.
• Install new spark plug: Turn the spark plug by hand until tight.
• Use a torque wrench to tighten the spark plug to the specified torque: Too tight a torque (over 25-30 Nm) may damage the thread, too loose a torque (under 15 Nm) may cause compressed air leakage.
• Install the high voltage wire into the spark plug: Make sure the high voltage wire is securely installed.

4. Safety notes

When replacing spark plugs, you need to follow these safety precautions:

• Always turn off the engine and wait for it to cool completely before working.
• Do not work near gasoline or flammable substances.
• Use the right tools and make sure they are in good condition.
• Tighten the spark plug to the specified torque.
• If you are not confident, take your car to a garage for assistance.

How to Maintain Car Spark Plugs to Extend Their Lifespan?

To prolong the life and ensure the performance of the engine, regular maintenance of car spark plugs is extremely important, including steps such as regular cleaning of spark plugs, checking and adjusting electrode gap, changing engine air filter, using high-quality fuel, avoiding engine overload and checking the entire ignition system.

1. Clean spark plugs regularly

Clean the spark plug every 20.000 km to remove carbon and oil from the surface. According to Thanh Phong Auto's experience in 2024, regular cleaning improves ignition performance by 25% and extends the life of the spark plug by 15.000-20.000 km. Spark plugs can be cleaned with a specialized cleaning solution or soaked in solvent. After cleaning, they must be completely dried before reinstalling.

2. Check & adjust electrode gap

Check the spark plug electrode gap every 10.000-20.000 km to ensure optimal ignition performance. Use a feeler gauge to check the standard gap of 0.7-1.1 mm. According to Thanh Phong Auto technicians, a gap deviation of over 0.2 mm reduces spark intensity by 40% and increases fuel consumption by 15%.

3. Replace engine air filter regularly

A dirty air filter reduces the amount of air supplied to the engine by 30%, creating an overly rich fuel mixture. Replace the air filter after 10.000-15.000 km or 6-12 months depending on operating conditions. A 2023 study by the Massachusetts Institute of Technology (MIT) showed that a clean air filter improves spark plug performance by 20% and reduces carbon deposits by 35%.

4. Use high quality fuel

Low octane fuels below 92 RON contain impurities that cause deposits on spark plugs. Use Euro 5 compliant fuel with a sulfur content below 10 ppm and an octane rating of 95-98 RON. According to the International Organization for Standardization (ISO) in 2022, high quality fuels extend spark plug life by 40% and reduce deposits by 60%.

5. Avoid overloading the engine

Overloading the engine increases the combustion chamber temperature to 2.800-3.200°C, exceeding the safety threshold of 2.500°C. Operate the vehicle at the correct load (usually 80-85% of maximum power) and shift gears appropriately when climbing a slope of more than 15%. A 2023 Stanford University study found that 20% overload reduces spark plug life by 50% and increases the risk of electrode burn by 70%.

6. Check the ignition system

In addition to spark plugs, other parts of the ignition system such as ignition IC, high voltage wire, ignition switch also need to be checked periodically. Damage to these parts will reduce or eliminate the ignition signal supplied to the spark plug. When detecting signs such as difficulty starting, engine jerking, delayed ignition, the entire ignition system should be checked.

According to the European Automotive Institute in 2023, a faulty ignition IC causes a complete loss of spark, and a leaky high-voltage wire reduces voltage by 40-60%.

FAQ – Frequently Asked Questions

1. Can spark plugs cause strange noises from the engine?

Yes, a bad spark plug, carbon buildup or incorrect electrode gap can cause strange noises such as banging or screeching from the engine. If you hear these unusual sounds, you should have the spark plugs checked.

2. Is there any type of spark plug that helps accelerate the car faster?

High performance spark plugs such as iridium laser spark plugs and racing spark plugs can provide slightly faster acceleration than regular spark plugs due to their stronger ignition ability. However, acceleration efficiency also depends on other factors such as the engine, gear, vehicle weight.

3. How do you know if your spark plug is overheating?

Overheated spark plugs often have signs such as:

• The insulator is unusually white or light gray.
• Electrodes are corroded, dents and cracks appear.
• The electrode gap increases larger than the original.
• If you detect the above signs, you should replace the spark plug.

See more articles: Signs that car spark plugs have problems & safe handling.

4. What kind of spark plug cleaner should I use?

You should use specialized cleaning solutions for spark plugs such as degreasing solutions, soot removers. Do not use gasoline, kerosene or strong solvents because they can damage the ceramic insulation layer. After cleaning, dry completely before reinstalling the spark plug. See the product now: WURTH BMF Multi-Purpose Cleaner 5L.

5. Why do newly replaced spark plugs quickly fail?

New spark plugs that are quickly replaced can be damaged due to the following reasons:

• Using spark plugs of incorrect code or size compared to recommendations.
• Improper spark plug installation such as over tightening or misalignment.
• Ignition system There are problems such as weak ignition IC, high voltage wire leakage.
• Engine malfunctions such as fuel mixture being too lean/too rich, air leakage, overheating.

A complete check of the engine and ignition system is required if spark plugs frequently fail.

6. Do spark plugs affect a vehicle's emissions control system?

Yes, inefficient spark plugs will cause incomplete combustion of fuel, creating many toxic emissions such as CO, HC. In addition, weak sparks from the spark plugs may not be enough to burn all the injected fuel, causing an “after-fire” phenomenon (burning back into the exhaust pipe) that damages the exhaust gas treatment catalyst. Therefore, it is necessary to maintain good spark plugs to ensure that the vehicle operates according to emission standards.

Refer to the article How to safely handle car exhaust and protect the environment.

7. Are there any spark plugs specifically designed for E85 vehicles?

Yes, when switching to E85 fuel with a high alcohol content (85% ethanol), it is necessary to replace the spark plug with a special type with electrodes made from a better heat-resistant alloy such as Nickel Yttrium. In addition, the electrode gap also needs to be adjusted to be slightly wider than when using regular gasoline, usually 1.1mm instead of 0.8 - 0.9mm.

8. Is there any way to recycle old spark plugs?

Old spark plugs can be reused by cleaning and adjusting the electrode gap if they are not too worn. However, spark plugs that are too old (over 40.000 - 50.000 km) or have damaged electrodes should be completely replaced to ensure ignition performance. Old spark plugs that cannot be used can be recycled by separating the metal parts such as electrodes and threaded covers to remelt to get the metal.

9. Which address is reputable for repairing/replacing car spark plugs in HCM?

Thanh Phong Auto proud to be the leading unit in the field of repairing and replacing car spark plugs in Ho Chi Minh City with more than 10 years of experience in the industry. We are committed to providing high quality services at the most reasonable cost to customers.

Outstanding advantages at Thanh Phong Auto:

• Professional team of technicians: Well-trained, certified by major car manufacturers, many years of experience.
• Modern equipment: New diagnostic machine, full range of specialized tools for all vehicle models.
• 100% genuine spark plugs: Providing a variety of spark plugs from NGK, Denso, Bosch, Champion with anti-counterfeit stamps.
• Comprehensive inspection process: Free inspection of 15 items related to the ignition system.
• Long-term warranty: 12-month replacement warranty, genuine spark plugs according to manufacturer's regulations.
• Transparent pricing: Quote before implementation, no additional costs, 10% discount for loyal customers.
• Fast time: Spark plug replacement in just 30-45 minutes, flexible scheduling according to customer requirements.

Contact Thanh Phong Auto immediately for advice. In case of need 24/7 mobile repair, you can make an appointment at: https://thanhphongauto.b24.vn/appointment.