[Automotive Knowledge] Symptoms and common causes of spark plug failure

As the editor, I'll explain the signs and common causes of spark plug failure from a Hong Kong driver's perspective , starting with the working principle, explaining the symptoms of a malfunction, and the impact of Hong Kong's climate and driving environment on the spark plug. I'll also teach you how to identify spark plug conditions and prevent them, so you don't have to wait until your engine shakes like a washing machine that knows something's wrong.

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1️⃣ What is the fire nozzle used for?

The spark plug is the ignition core of a gasoline engine . It is located at the top of the cylinder and is responsible for converting the high voltage electricity (up to 20,000–40,000 volts) sent by the ignition coil into a spark to ignite the fuel and air mixture in the cylinder.

A burner must:

• High temperature resistance (up to 800°C–1000°C)
• Maintaining a stable spark
• Resistant to combustion residues, oil and moisture

💡 Editor's note : The spark plug is crucial to fuel consumption, engine output and smoothness. A broken one will cause the entire engine to malfunction.

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2️⃣ Signs of nozzle failure (common in Hong Kong)

The following symptoms may not all occur at the same time, but if more than 1-2 of them occur, it is likely that you have a problem:

2.1 Difficulty starting a cold engine

• In the morning, I had to spin the key a few times before it would work, or sometimes I couldn't even get it to work.
• Cause: Carbon deposits on the nozzle or the gap becomes larger, and the spark voltage is insufficient.

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2.2 Engine shaking/unstable idling

• In P or N gear, the steering wheel vibrates slightly and the speed fluctuates.
• Idling at a red light for a long time will cause noticeable "slippage".
• Cause: Incomplete ignition of some cylinders, resulting in unbalanced power output.

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2.3 Weak acceleration

• When starting from a standstill or overtaking at high speed, the response is slow and the acceleration is not smooth.
• Reason: The ignition efficiency is low and the mixture cannot be completely burned.

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2.4 Sudden Knock/Spark Loss

• The car suddenly sinks while driving, as if someone is pulling you up.
• Occasional jerking sensation at high speeds.

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2.5 Increased fuel consumption

• The original range of 500 kilometers on a tank of fuel suddenly dropped to around 450 kilometers.
• Reason: Incomplete combustion, the computer adds fuel to maintain power → more fuel consumption.

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2.6 Abnormal exhaust

• Black smoke when starting or accelerating (excessive unburned oil)
• Smell of unburned gasoline when the car is cold

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💡Editor 's Hong Kong observation :
Local car owners often use short urban routes (for example, from Kwun Tong to Kowloon Bay). If the ignition nozzle does not reach the operating temperature for a long time, carbon deposits will accumulate particularly quickly, causing the above symptoms to appear earlier.

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3️⃣ Common causes of spark plug wear (Hong Kong drivers should pay special attention)

3.1 Natural wear and tear

• The nozzle electrode is subjected to long-term high temperature, the metal is gradually consumed, and the gap naturally becomes larger
• Ordinary nickel alloy nozzle life: 20,000-30,000 kilometers
• Iridium/Platinum spark plug life: 80,000-100,000 km

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3.2 Engine oil leaks into the combustion chamber

• The piston ring or valve oil seal is aging, the engine oil burns into the cylinder, and black oily carbon deposits form on the surface of the spark plug.
• Common in Hong Kong : Parking at the beach + high humidity, rapid aging of mechanical parts

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3.3 Poor fuel quality

• Inferior oil or long-term use of fuel containing high impurities will produce conductive carbon deposits after combustion, which will cause short circuit sparks.
• Although the fuel quality in Hong Kong is generally good, some car owners may encounter

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3.4 Long-distance and short-distance

• The flame can be extinguished before the nozzle reaches high temperature, and the carbon deposits produced by combustion will not be burned away
• Local drivers travel several kilometers a day, which consumes the life of the nozzle very quickly.

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3.5 Cooling or fuel injection system failure

• When the cold engine has an overly rich mixture that enters the combustion chamber for a long time, more carbon deposits will form.
• Injector oil leakage or computer mixture ratio adjustment error will cause the spark plug to burn black

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3.6 The nozzle model or calorific value is incorrect

• The calorific value is too cold: carbon deposits are difficult to burn and are prone to short circuits
• Too high calorific value: overheating, ablation, accelerated wear

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4️⃣ Factors that shorten the life of nozzles in Hong Kong

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5️⃣ How to Check the Status of the Fire Nozzle (DIY Basic Version)

Note : To check the nozzle, you need basic tools and be careful, otherwise the teeth may be damaged.

tool

• Spark plug (usually 16mm or 21mm)
• ratchet wrench
• Feeler gauge

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step

1. Remove the spark plug when the car is cold
2. Observe the color with naked eyes:
   • Brown/Light Gray → Normal
   • Black dry carbon deposits → Too rich mixture, long-distance short trip
   • Black oily carbon deposits → Oil blowby
   • White or electrode erosion → Overheating or premature ignition
3. Measure the electrode distance using a gap gauge: Compare with the factory specifications (the distance will increase when the wear is greater)

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💡Editor 's reminder :

• Hong Kong is humid, so if you don't remove the nozzle for a long time, it may oxidize slightly. → Remember to use appropriate torque when operating.
• If there are obvious cracks, electrode ablation, or ceramic damage, it must be replaced immediately.

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6️⃣ How to prevent premature nozzle failure (Hong Kong version)

1. Replace according to the manufacturer's recommended replacement cycle : Don't delay too long

   • Nickel alloy: 20,000–30,000 km
   • Iridium/Platinum: 80,000–100,000 km (Hong Kong is humid and has many short trips, so it is recommended to replace it 10–20% earlier)

2. Regular long-distance driving in high temperatures

   • At least once a week, take a 20-30 minute long-distance trip (with a larger throttle) to burn off the carbon deposits.

3. Maintain fuel quality

   • Avoid fuel of unknown origin
   • Occasionally use fuel system cleaner

4. Checking oil consumption

   • Prevent oil from entering the combustion chamber

5. Change the model and calorific value

   • Follow the manufacturer's recommendations and avoid random upgrades or downgrades.

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7️⃣ Editor’s final summary

Although the spark plug is a delicate component, its failure will have a chain effect on fuel consumption, output, cold start and comfort.

If Hong Kong drivers make many short trips, drive at many traffic lights, or use the air conditioner for a long time in the summer , the ignition nozzle will age significantly faster than the data in the specifications. So don't just stick to the official mileage, but check it in advance based on your driving habits.

Remember, a bad spark plug will reduce the efficiency of the entire cylinder. It is not as simple as just reducing power. Long-term carbon deposits may damage the catalyst, and the final repair cost may be thousands or even tens of thousands of dollars.