Q: Smell gasoline and see black smoke from exhaust

Hello. Black smoke from the exhaust is the first sign of a rich condition. This means too much fuel is entering the engine. This can be caused by a number of reasons from a leaking fuel injector to a failing sensor. In some drastic cases, it can even be an internal engine failure. A mechanic would typically install a computer scan tool that reads engine data to see what the sensors are seeing. This will let them know if a sensor is reading incorrectly. If not, then it may be a fuel injector that is stuck open. The best place to start is with a scan tool so that you do not replace any parts that are not needed. If you do not have a scan tool, then you should enlist the assistance of a certified mechanic to scan for fault codes and replace any failing parts.