The internal combustion engine requires a precise mixture of fuel and air to run correctly. Too much of either can result in severe running issues. When your engine idles rough and the exhaust has the smell of raw, unburned gasoline, it is suffering from a rich condition or or incomplete combustion. There are four main component failures that can result in this condition.

Fouled or Worn Out Spark Plugs

Over time, or due to mechanical problems, the spark plugs in your vehicle wear out or foul. The actual act of a spark plug wearing out is when the electrode wear out, widening the spark plug’s gap. A widened gap causes a colder spark, which can create incomplete combustion, as it cannot burn all of the fuel in the combustion chamber.