Performance Issues:
* Misfires: This is the most common symptom. A misfire occurs when a spark plug fails to ignite the air-fuel mixture in the cylinder. This leads to rough idling, hesitation during acceleration, and a loss of power. You might hear a sputtering or popping sound from the engine.
* Poor Acceleration: The engine struggles to produce the necessary power, resulting in sluggish acceleration.
* Reduced Engine Power: Overall power output is significantly diminished.
* Stalling: In severe cases, the engine might stall, particularly at idle or low speeds.
Fuel Economy Issues:
* Decreased Fuel Efficiency: Misfires and incomplete combustion waste fuel, leading to significantly lower gas mileage.
Emissions Issues:
* Increased Emissions: Incomplete combustion produces more pollutants, leading to higher emissions of unburnt hydrocarbons, carbon monoxide, and nitrogen oxides. This can result in failure of emission tests.
Engine Damage:
* Catalyst Damage: Unburnt fuel passing through the catalytic converter can overheat it and damage it. This is an expensive repair.
* Pre-Ignition/Detonation: A faulty plug can lead to pre-ignition or detonation (knocking), where the air-fuel mixture ignites before the spark plug fires, causing significant damage to engine components like pistons and connecting rods.
Other Problems:
* Check Engine Light: The car's onboard computer will usually detect misfires and illuminate the check engine light.
* Hard Starting: It might be harder to start the engine, particularly in cold weather.
It's crucial to address bad spark plugs promptly. While they're relatively inexpensive to replace, neglecting the problem can lead to costly repairs down the line.
