What Color of Spark Plug Indicates a Fault?
2 Answers
Spark plugs turning black is a sign of a fault. The blackening occurs due to an overly rich air-fuel mixture, requiring timely cleaning or replacement of the spark plug. Steps for replacing spark plugs: Open the engine hood, lift the plastic cover of the engine, remove the high-voltage distributor wires, and mark each cylinder's position to avoid confusion. Use a spark plug socket to remove the spark plugs one by one. While removing, check for any external debris like leaves or dust and ensure thorough cleaning. Place the new spark plug into the spark plug hole, hand-tighten it a few turns, then use the socket to tighten it further. Reinstall the high-voltage distributor wires according to the firing order and secure the cover. Spark plug replacement intervals: Under normal maintenance conditions, spark plugs should be replaced every 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so it's advisable to follow the user manual. The following standards can be referred to for maintenance replacement: Platinum spark plugs should be replaced at 40,000 kilometers, standard nickel alloy spark plugs at 20,000 kilometers, and iridium spark plugs between 60,000 to 80,000 kilometers.
I've encountered spark plugs turning black before, dark as if dipped in ink—that's definitely a sign of trouble. The engine shook violently during startup, and upon inspection, it turned out to be caused by an overly rich air-fuel mixture—too much fuel and too little air, leading to incomplete combustion and carbon buildup. If the color is oily and wet, it's likely due to engine oil leakage burning off, requiring checks on piston rings or valve seals. Grayish-white or melted electrodes are even scarier, indicating excessive temperature or an imbalanced air-fuel ratio prone to knocking. During every maintenance session, I take time to inspect the spark plugs—they should normally be a light tan color. I recommend car owners not overlook this detail; early detection can save big money. Otherwise, prolonged neglect leading to engine damage will burn a hole in your wallet.
