Maybe your piston ring or valve leaking. If this is a problem than you might want to do a top overhaul.

This post has been edited by Civil: Dec 23 2006, 02:41 PM

White smoke: White smoke is caused by water and or antifreeze entering
the cylinder, and the engine trying to burn it with the fuel. The white
smoke is steam. There are special gaskets (head gaskets are the primary
gaskets) that keep the antifreeze from entering the cylinder area. The
cylinder is where the fuel and air mixture are being compressed and
burned. Any amount of antifreeze that enters this area will produce a
white steam that will be present at the tailpipe area.

If white smoke is present, check to see if the proper amount of
antifreeze is inside the radiator and the overflow bottle. Also check to
see if antifreeze has contaminated the engine oil. You can look at the
engine oil dipstick, or look at the under side of the engine oil filler
cap. If the oil is contaminated with antifreeze, it will have the
appearance of a chocolate milkshake. Do not start the engine if the oil
is contaminated with antifreeze, as serious internal engine damage can
result.

How did antifreeze get in the oil or cylinder in the first place? The
engine probably overheated and a head gasket failed due to excessive
heat, thus allowing antifreeze to enter the cylinder (Where it is not
meant to be).

Blue Smoke: Blue smoke is caused by engine oil entering the cylinder area
and being burned along with the fuel air mixture. As with the white
smoke, just a small drop of oil leaking into the cylinder can produce
blue smoke out the tailpipe. Blue smoke is more likely in older or higher
mileage vehicles than newer cars with fewer miles.

How did the engine oil get inside the cylinder in the first place? The
car has many seals, gaskets, and O-rings that are designed to keep the
engine oil from entering the cylinder, and one of them has failed. If too
much oil leaks into the cylinder and fouls the spark plug, it will cause
a misfire (engine miss) in that cylinder, and the spark plug will have to
be replaced or cleaned of the oil. Using thicker weight engine oil or an
oil additive designed to reduce oil leaks might help reduce the amount of
oil leaking into the cylinder.

Black Smoke: 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.

I hope this helps you determine what could be causing your engine smoke,
and the possible reasons behind the smoke.

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