Sounds like that spark plug isn't firing. Sometimes they're just bad. A black coating on the tip is caused by unburnt fuel. That popping in the exhaust us the unburnt fuel igniting from coming into contact with the hot exhaust pipe. You will notice the same thing with very rich running performance cars. Put that plug in a different cylinder and see what happens. Could also be a compression problem. How many miles are on it?
Edit to add: Is the plug gapped correctly? Should be at 0.56. The plug could have also been fouled by too much fuel caused by a faulty injector. Swap the plug and wire with another cylinder and see what happens.
[This message has been edited by RilesOfSmiles (edited 12-27-2013).]