Is a Blackened Spark Plug Indicative of Over-Rich Air-Fuel Mixture?
2 Answers
A blackened spark plug is caused by an over-rich air-fuel mixture, which requires timely cleaning or direct replacement of the spark plug. Steps for replacing a spark plug: 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 them, check for external debris such as leaves or dust and ensure thorough cleaning. Place the new spark plug into the spark plug hole, hand-tighten it a few turns, and then use the socket to tighten it further. Reinstall the removed high-voltage distributor wires in the firing order, and secure the cover. Spark plug replacement interval: Under normal maintenance conditions, replacement is recommended after driving 40,000 to 60,000 kilometers. However, this may vary depending on the brand and engine type, so it's advisable to follow the owner's manual. The following standards can serve as a reference 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 at 60,000 to 80,000 kilometers.
I've encountered cases where the spark plugs turned black, which is indeed often a sign of an overly rich air-fuel mixture. A rich mixture means too much gasoline and too little air, resulting in incomplete combustion that leaves black carbon deposits on the spark plugs. Last time my car's fuel consumption skyrocketed, and upon inspection, we found the oxygen sensor had failed, causing excessive fuel injection and completely blackened spark plugs. Additionally, a clogged air filter or faulty fuel injection system can cause the same issue. To confirm, it's best to connect a diagnostic tool to read the data stream and check if the air-fuel ratio is too high. After fixing the issue and replacing the spark plugs, the car returned to normal. Remember, regular checks of these components can prevent trouble.
