Spoon Sports 11/3/2011Black smoke is caused by excess fuel that has entered the cylinder area and cannot be burned completely. Another term for excess fuel is "running rich." Poor fuel mileage is also a common complaint when black smoke comes out of the tailpipe. Black smoke out the tailpipe is the least cause for alarm. Excess fuel will usually effect engine performance, reduce fuel economy, and produce a fuel odor.
How did the fuel get into the cylinder in the first place? Some of the causes of excess fuel are a carburetor that is out of adjustment, a faulty fuel pump, a leaky fuel injector, or a faulty engine computer or computer sensor. If black smoke is present, check the engine oil as in the white smoke example to make sure excess fuel has not contaminated it. Do not start the engine if a heavy, raw fuel smell can be detected in the engine oil.
MasterTech 11/3/2011A first thing to start with would be to check the engine temp while running. If the engine is running cold, the computer will adjust the fuel mixture rich (like a choke). If the temp is good, next check the CTS (coolant temp sensor). The CTS tells the computer how cold or hot the engine is and adjusts the fuel mixture accordingly. If the temp is good but the sensor reads cold, then you can get a rich fuel mixture. The injectors in the throttle body (common to leak), would be another place to inspect to make sure they are flowing evenly and not dripping into the intake manifold. You can have the injectors flow tested and/or rebuilt if needed.