How to judge whether the car spark plugs need to be replaced?

1. Pay attention to the vehicle's driving performance.

When the performance of the spark plugs deteriorates, your car will tell you through some "symptoms", which is the most direct signal. 

(1) Difficulty starting and ignition is not smooth

This is the most common early sign. You will find that the starter motor sounds like it is turning for a long time, but the engine needs to try many times before it can ignite successfully, or it feels more "labored" than usual. This is because the ignition energy of the spark plug is insufficient and cannot reliably ignite the mixture. 

(2) The body shakes significantly at idle speed

When you are parked and waiting (such as waiting for a red light), the engine should run smoothly under normal circumstances. If you feel irregular and irregular shaking from the steering wheel or the entire body, it is likely that the spark plugs of one or more cylinders are not working properly, resulting in unbalanced engine work and thus shaking. 

(3) Weak acceleration and increased fuel consumption

When you step on the accelerator, the car feels sluggish and the speed increases very slowly, especially when going uphill or when you need to accelerate quickly. At the same time, you may find that the mileage you have traveled on a tank of gas has decreased significantly recently. This is because the old spark plugs have reduced ignition efficiency, resulting in incomplete fuel combustion and inability to effectively convert energy into power. 

(4) Jamming during driving

When driving at a constant speed or accelerating slowly, the vehicle will suddenly experience a jerking sensation, and the power will feel discontinuous. In severe cases, the exhaust pipe may even make a "pop" sound due to the burning of unburned gasoline inside.

2. Follow official maintenance recommendations

Regardless of whether the vehicle has the above-mentioned feeling, the most scientific method is always to follow the recommended replacement cycle given by the manufacturer in the "Owner's Manual". The life of spark plugs made of different materials varies greatly. Ordinary nickel alloy spark plugs: Short life, generally need to be checked and replaced after 20,000-30,000 kilometers. Platinum spark plugs: The original configuration of many models now has a longer life, and the recommended replacement cycle is usually 40,000-60,000 kilometers. Iridium spark plugs: Better performance, longer life, and the replacement cycle can reach 80,000-100,000 kilometers. Therefore, the first step should be to check your car maintenance manual. If the mileage has reached or exceeded the cycle specified in the manual, even if the car does not feel abnormal when driving, it is recommended to replace it because its performance has declined unnoticed.

3. Perform actual disassembly inspection

If symptoms occur or the cycle is reached, the most reliable method is to remove a spark plug and take a look. There are two main points to look at: 
(1) Check the electrode gap Use a professional gap gauge to measure the gap between the center electrode and the side electrode. If this gap is significantly larger than the standard value specified in the manual (usually 0.8mm-1.2mm), it means that the electrode has been burned by the high-temperature arc and must be replaced. Too large a gap will cause ignition difficulties or even misfires. 

(2) Check the combustion status and deposits Healthy status: The electrode part is light brown or grayish white, relatively clean, and without too much deposits. Status that requires attention: Severe carbon deposits: The electrode and ceramic insulator are covered with a layer of black, velvety carbon deposits. This may be caused by an overly rich mixture or long-term low-speed driving. It can be cleaned and re-inspected, but it needs to be replaced if it is serious. Oil stains: The spark plug head looks wet and has oily residue. This is a dangerous signal, usually indicating that the engine has an oil burning problem and needs to be repaired at the same time. Severe ablation: The electrode has been burned out of shape, rounded, or even cracked in the ceramic body. This indicates that the spark plug has reached the end of its life and must be replaced immediately.