How to Know When to Replace Spark Plugs

[JohnFitz]

Methods to determine if spark plugs need replacement are: 1. When the surface of the spark plug shows severe burning, cracking, or electrode melting, it indicates the spark plug has reached the end of its lifespan and needs replacement; 2. Keep the car idling. If the engine exhibits intermittent or continuous shaking and emits abnormal "popping" sounds, it suggests a possible issue with one of the spark plugs, which then requires replacement. Spark plugs, commonly known as igniters, function by discharging high-voltage pulses from the ignition wires, breaking down the air between the two electrodes to generate an electric spark, thereby igniting the air-fuel mixture in the cylinder.

[LeJuniper]

Having driven for many years, I often encounter spark plug issues. Here are a few methods to diagnose them: If the engine struggles to start or idles roughly, shaking like a tractor, it’s likely due to aging spark plugs; a sudden spike in fuel consumption is also a sign—if a full tank used to last 500 km but now only 400, it’s time for a check. You can inspect the spark plugs yourself—pull them out and check the electrode gap, which should be 0.8-1.2 mm; if it’s too wide or has carbon buildup, they need replacing. Also, listen for sounds—if acceleration feels uneven and the engine seems to gasp, ignition is failing. It’s recommended to replace them by mileage, typically every 30,000-50,000 km or as per the manufacturer’s manual. Delaying replacement can affect overall performance, increase repair costs, and compromise safety—don’t overlook these small details.

[StKylie]

As a novice driver just starting to learn car maintenance, I know that delaying spark plug replacement makes the car act up: for example, it takes several attempts to start the engine when cold, which is quite frustrating; poor acceleration on the road makes overtaking difficult; checking spark plugs is simple—just remove them with a socket tool and look for oil stains or cracks, and an excessively large gap indicates severe wear; I've tried replacing them myself, which is low-cost but saves on repair fees; a daily driving fuel consumption increase of over 10% is a clear warning; regular inspections every 2-3 years, combined with mileage intervals, are recommended; installing new ones can improve engine efficiency and prevent damage to other components like coils, and learning DIY skills can be quite fun.

[DelParker]

I mainly drive to pick up and drop off my family, so safety is the top priority. The risk of spark plug failure is not small: once on the highway, the engine warning light came on, and the inspection revealed that the spark plug gap had widened, causing ignition failure. Symptoms include unstable idling, slight vibrations felt inside the car, and difficulty starting, especially in cold weather when it takes several attempts to start. For self-inspection, rely on visual checks—if the spark plugs are burnt or have carbon buildup, it's a sign they've reached the end of their lifespan. It's recommended to have them checked during annual maintenance, as dealerships use diagnostic tools for more accurate results. Failing to replace them promptly can increase the risk of accidents and affect fuel efficiency, leading to higher fuel costs. I usually keep a log and replace them around every 50,000 kilometers to ensure the car is reliable and hassle-free.