What Are the Symptoms of a Bad Spark Plug?
3 Answers
If a spark plug exhibits the following symptoms, it may indicate a malfunction: Difficulty in starting the car, whether cold or hot, often requiring multiple attempts. Engine shaking, noticeable while driving. Reduced power, feeling significantly weaker than usual. Increased fuel consumption. Stalling issues. Failed exhaust emissions. Common causes and diagnosis of spark plug failures: There are several common reasons why a spark plug may fail to work: 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 electrode's flame-quenching effect, resulting in weak sparks and difficulty igniting the mixture. A gap that is too large may exceed the ignition system's voltage capacity, preventing sparking between the electrodes. Cracked spark plug skirt. High-voltage current leaks through the crack, preventing sparking at the electrodes. Electrode carbon buildup, causing the center electrode to leak current to the surroundings instead of sparking to the side electrode. Excessive carbon buildup can short-circuit the spark plug, preventing sparking 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 sparking. 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 the high-voltage wire. A leak in the wire from the ignition coil to the distributor can prevent the entire engine from starting, while a leak from the distributor to a spark plug can prevent sparking in one cylinder. Burnt platinum contacts. This can prevent all spark plugs from sparking, making the engine unable to start or run normally. Faulty spark plugs should be replaced promptly. The replacement steps are as follows: Open the hood and remove the engine's plastic cover. Disconnect the high-voltage wires, marking their positions to avoid confusion. Use a spark plug socket to remove each spark plug, checking for and cleaning any debris like leaves or dust. Insert the new spark plug into the hole, hand-tightening it first before using the socket. Reinstall the high-voltage wires in the correct firing order and replace the cover. Spark plug replacement interval: Typically, they should be replaced every 40,000-60,000 km under normal maintenance conditions, but this may vary by brand and engine. Always refer to the owner's manual for guidance.
Having driven my old car for so many years, I'm all too familiar with spark plug failures. Starting the car becomes extremely difficult, especially in cold weather, with the engine sputtering for a long time before it finally turns over. Once on the road, you can clearly feel severe body vibrations, and the steering wheel shakes noticeably at idle—making stop-and-go city driving even more frustrating. Acceleration feels sluggish, with the car making a muffled, choking sound even when you floor the gas pedal, as if it's stuck. Fuel consumption spikes noticeably, and frequent trips to the gas station become a headache. Thick black smoke billows from the exhaust pipe, emitting a pungent odor. Once, I nearly broke down on the road because of this issue—a hard lesson that taught me to check spark plug gaps every 10,000 km and replace them promptly to keep the engine running smoothly and durably. If neglected for too long, cylinder pressure can drop, doubling repair costs. For seasoned drivers, this is not something to take lightly.
As a seasoned car enthusiast, a faulty spark plug immediately gives itself away. Starting the car often fails, requiring multiple attempts before it kicks in; at idle, the engine shakes violently, making the car feel like it's in an earthquake; pressing the accelerator yields weak acceleration, making overtaking difficult and highway driving unstable; fuel consumption spikes, draining your wallet quickly; the engine light suddenly illuminates on the dashboard, indicating an ignition fault. Don't underestimate this small component—black smoke from the exhaust signals incomplete combustion and environmental harm. I've tried replacing them myself; you need to check the electrode condition: darkening indicates heavy carbon buildup and weak sparks. It's advisable to use high-quality fuel regularly and not wait until the problem becomes severe, or the catalytic converter will suffer as well.
