How to Determine the Quality of Spark Plugs?
4 Answers
Spark plugs exhibit the following symptoms when they may be faulty: Difficulty starting the car, both during cold starts and hot starts, often requiring multiple attempts. Engine shaking, where the car experiences vibrations while driving. Reduced power, noticeably weaker performance compared to normal conditions. Increased fuel consumption. Stalling issues. Failed exhaust emissions. Common causes and diagnosis of spark plug failures: Several common issues can cause spark plugs to malfunction: Incorrect spark plug gap adjustment. A gap that is too small limits the contact area between the spark and the air-fuel mixture and suppresses flame kernel growth due to the quenching effect of the electrodes, resulting in weak sparks and difficulty igniting the mixture. A gap that is too large may exceed the ignition system's voltage capacity, preventing a spark from jumping between the electrodes. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing sparks from jumping between the electrodes. Carbon buildup on the electrodes, causing leakage from the center electrode to the surrounding area instead of jumping to the side electrode. Excessive carbon deposits can short-circuit the spark plug, preventing sparks and damaging the insulator. Damaged electrodes. Prolonged electrical erosion from sparks or chemical corrosion from combustion gases can cause electrodes to break or detach, preventing sparks. Low insulation resistance of the spark plug. This reduces the ignition voltage applied to the spark gap, weakening or completely disabling the spark. Short circuit in high-voltage wires. Leakage in the wire from the ignition coil to the distributor can prevent the entire engine from starting, while leakage in the wire from the distributor to the spark plug can prevent a single cylinder's spark plug from firing. Eroded platinum contacts. This can cause all spark plugs to fail, preventing the engine from starting or running normally. Faulty spark plugs should be replaced promptly. The replacement steps are as follows: Open the engine hood, remove the plastic cover, and disconnect the high-voltage wires, marking each cylinder's position to avoid confusion. Use a spark plug socket to remove each spark plug, ensuring the surrounding area is free of debris like leaves or dust. Insert the new spark plug into the hole, hand-tighten it a few turns, and then use the socket to tighten it fully. Reinstall the high-voltage wires in the correct firing order and reattach the cover. Spark plug replacement interval: Typically, spark plugs should be replaced every 40,000-60,000 km under normal maintenance conditions, but this may vary by brand and engine type. Always refer to the owner's manual for specific recommendations.
I do a lot of car repairs myself, and when it comes to judging the condition of spark plugs, there are several aspects to check. First is the appearance—after pulling out the spark plug, inspect the tip of the electrode. If there are signs of burning, blackening, or browning, it’s likely due to carbon buildup or severe wear; a normal spark plug should be grayish-white or light brown. Next, measure the electrode gap using a small caliper or feeler gauge—the gap is usually around 0.6 to 1.0 mm, and anything too large or too small is no good. If your engine shakes noticeably during long drives, idles roughly, or suddenly consumes more fuel, it might be a spark plug issue. Before replacing spark plugs, I also test the spark with a simple tool—attach a spark plug wrench to the ignition wire and check for a blue spark; no spark indicates poor insulation. In short, simple DIY checks can save a lot on repair costs. Remember to inspect your spark plugs every 30,000 km—don’t wait until major problems arise. Oh, and when buying spark plugs, always choose reputable brands—don’t skimp on quality, as it can affect engine longevity.
I learned this from working on car projects, and judging whether a spark plug is good or bad is quite simple. First, do you feel anything unusual while driving? For example, sluggish starts, rough acceleration, or black smoke from the exhaust pipe—these are signs that the spark plug is faulty. Second, pull out the spark plug and inspect it closely. If the electrode tip appears yellowed, whitened, or is wet with gasoline, it indicates spark plug leakage or poor ignition; a healthy spark plug should be clean and dry. I usually use an old coin as a makeshift gauge to measure the electrode gap—around 0.7-1 mm is ideal. If you're unsure, buy a spark plug tester to check the current strength; replace it if the reading is weak. When replacing spark plugs, don’t forget to clean the installation hole, as dirt buildup can accelerate wear. I’ve encountered misfires caused by spark plug issues several times, so regular self-checks are crucial, especially before long highway trips. Many modern cars use long-life spark plugs, which only need replacement every 50,000 kilometers.
I drive my kids to and from school, and the condition of the spark plugs is crucial for safety. The method to check isn't complicated: first, if the engine jerks or struggles to start while driving, consider whether the spark plugs might be faulty; second, during regular oil changes, have the mechanic inspect them, or buy new spark plugs to compare colors—if the old ones have blackened or deformed electrodes, they need replacing. Don't overcomplicate it; the key is to act promptly. Spark plug issues may seem minor but can damage the car and increase fuel consumption if neglected. I keep a small wrench in my car to check the spark plugs in emergencies. A healthy spark plug should be clean and free of stains, with uniform gaps. I keep a maintenance log, and spark plugs typically last about 30,000 kilometers. Remember, safety comes first.
