I have a 92 blazer 4.3 vortec
Black 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. Call your mechanic and
advise him of what you have found.
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