Basically there are three different kinds of smoky auto exhaust--blue smoke, white smoke or black smoke. The repairs you need to make to your car are vastly different depending on the color of the smoke leaving your tailpipe. Whether you will be able to make the repairs to your vehicle yourself or not depends on the color of the smoke and on your skill and desire to make repairs to your engine. Even if you choose to have your engine looked at by a professional, diagnosing the problem yourself will give you some control over the repair process and make you a more knowledgeable consumer.
Look at the smoke coming out of your tailpipe when your engine is warm. Keep in mind that white smoke coming out of your tailpipe on a cold morning before your engine warms up may mean nothing--you must wait for the engine to reach its normal operating temperature before assessing the color of the tailpipe smoke.
Rev your warm engine slightly. White smoke coming from your tailpipe means that water has entered your combustion chamber--often through a blown head gasket or even a cracked cylinder block. This is a major problem.
Wait for your engine to cool and then remove the radiator cap by turning it 1/4 to 1/2 turn counter clockwise. Check your coolant level. A drop in the water in your radiator will verify a cracked head or blown gasket. The cylinder heads will need to be removed and inspected and the cylinder heads will need to be pressure tested for cracks. This can only be done at a properly-equipped machine shop.
Inspect your fuel injector if black smoke comes out of your tailpipe. Black smoke indicates that too much fuel is being burned. You may need a new fuel injector or your car's computer system could be malfunctioning.
Take your vehicle to a machine shop and have the computer system tested. If the computer system is working correctly then replace the fuel injector.
Plan on a ring job (replacing the piston rings) if blue smoke is coming from your vehicle's tailpipe--blue smoke indicates that oil is getting into your combustion chamber. A ring job involves removing the cylinder heads of your engine and is a major job. If you are an experienced engine mechanic or if you know someone who is and is willing to help you, then plan on spending a whole day replacing your car's piston rings. Otherwise take you vehicle to a garage and have your compression pressure checked--low pressure indicates the need for new piston rings.
