Here's why:
* Rich mixture: A rich mixture means there is too much fuel and not enough air in the combustion process.
* Incomplete combustion: This excess fuel doesn't burn completely, resulting in unburnt hydrocarbons and soot particles.
* Black exhaust: These unburnt particles are what give the exhaust its black or dark gray color.
Other signs of a rich fuel mixture:
* Rough idling: The engine may struggle to run smoothly at idle.
* Reduced power: The engine may have less power than usual.
* Fuel odor: You might smell a strong fuel odor coming from the exhaust.
It's important to address a rich fuel mixture as it can damage the engine over time.
