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Black smoke is usually excess fuel, that can be caused by things such as leaky fuel injectors, bad coolant temp sensor, weak spark (bad coil?). You don't say what year or engine. If a carburetor, it may need overhaul. If excess fuel gets really bad, it can wash the oil off the piston rings and cause rings to wear, plus dilute engine oil causing bearing failure.
Oil burning or excess gas not being fully burned. If gas, smoke will be very black, whereas oil burning has a bluish tinge. If your engine runs good otherwise, it is probably oil burning. Most common cause of that is worn piston rings.
Black smoke: Black smoke is often a result of too much fuel and not enough air in the combustion chamber. In rare cases, it can be weak fuel pressure causing fuel to 'drip' from injectors rather than 'spray'. It can also be caused by weak fire in the combustion chamber.
Gray smoke: Gray smoke is caused by brake fluid. It generally means that your brake master cylinder is bad, and is getting sucked through the vacuum brake hose.
Blue smoke: Blue smoke is generally caused by the burning of an oil in the combustion chamber. Normal causes of oil getting into the combustion chamber are weak piston rings, bad valve guides, bad valve seals, or plugged up engines where oil is sucked back through PCV system,usually due to lack of oil changes
Smoke oil? For what your thinking that is oil? Smoke coming from the
tailpipe is not good news, but does not necessarily mean the engine
needs rebuilding. First, you need to determine what color of smoke is
coming from the tailpipe * 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. * 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. * 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.
If you confirm us that is oil smoke, check and keep in mind that 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
Your cat won't cause your vehicle to smoke, unless there is oil on it, then as the exhaust warms up, the cat will burn off the oil. Chances are, there is something wrong with your engine.
There are a few diagnostic steps you can make to see if you're burning oil, running rich, or have a leaking head gasket:
Check your plugs. If they've got oil or a filmy, soot-like deposit, you've got worn valve guide seals or worn rings, and you're burning oil, or you're running rich, indicative of other problems.
The exhaust "smoke" that you see, if it's like a white/gray cloud, could be steam from a leaking head gasket or water in the intake. If it's blue-ish, that's normally running rich. If it's black, you're probably burning oil.
Chances are if you are blowing blue smoke, you are burning oil. Another cause of blue tint smoke is you are burning to much fuel and not enough air. If the engine does not act erratic or acts like it is flooding out, then I would say you are burning oil. The most common problem found with burning oil is either worn piston rings, bad valve seats/seals. If the engine has high mileage, I would recommend any type of oil treatment. Change your oil, filter included, use some form of engine treatment, run it for a few hundred miles, and rechange your oil and filter again. If your engine has over 100,000 miles, I would highly recommend using an oil that is made for high mileage engines. As this oil has additives that will help ease the aging engine. If this doesn't work for you, I would say you need to have the rings and valve seals replaced. You can do this yourself with a little knowledge of engines and pick yourself up a Haynes Manual at your local auto parts store if you do not already have one. Hope this helps. Feel free to comment if you need more assistance. Please don't forget to rate. Thanks!
First you need to determine if it is actually black smoke or if it is blue smoke. There are three colors of smoke that can come from the tailpipe. It is not white smoke obviously because that is easily differentiated from blue or black and generally indicates water or antifreeze leaking past the head gasket and into the compression area of the motor. White smoke is the steam of the water/antifreeze being emitted
Blue smoke is caused by engine oil entering the cylinder area and being burned along with the fuel air mixture. As with 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. 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 plugs, 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 is caused by excess fuel that has entered the cylinder area and cannot be completely burned. 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 heavy fuel odour in the engine compartment. Some of the causes of excess fuel are a carburetor that is out of adjustment which is not likely unless you have installed an aftermarket carburated system on your non-carburated car, a faulty fuel pump, a leaky fuel injector, or a faulty engine computer or emissions sensor. If black smoke is present, check the engine oil 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. Check the above mentioned systems and after detecting the trouble replace the faulty parts and then the engine oil and filter.