Exhaust smoke system is the piping that directs the burned fuel out of the engine and to the back of the vehicle. Each cylinder has an exhaust port, the manifold goes over these ports. The gases travel into the manifold and head towards the back of the car. Close to the manifold, you will have a catalytic converter; uses special metals ‘catalysts’ to reduce emissions. Then some more pipe heading towards the muffler that muffles the sound of the engine, then a little more pipe out to the back of the car.
Blue/Gray Smoke: Blue/gray exhaust smoke is an indication of oil burning in the combustion chamber. These are possible symptoms and causes:
Valve Seals: Leaking valve seals will cause blue/gray exhaust smoke.
Valve Guides: Excessive clearance between the valve stem and the valve guide allows oil to leak past the gap into the cylinder.
Piston Rings: Worn or damaged piston rings will cause blow-by, resulting in blue/gray smoke.
Worn Cylinder Walls: Worn cylinder walls cause blow-by, resulting in blue/gray smoke.
PCV System: A stuck closed PCV valve causes excessive crankcase pressure, resulting in blue/gray smoke.
Black Smoke: Black exhaust smoke is an indication of a rich fuel condition. These are possible causes:
Fuel Injectors: A leaking or dripping fuel injector will cause a rich fuel condition.
Fuel Pressure Regulator: A stuck closed fuel pressure regulator will cause a rich fuel condition.
Fuel Return: A restricted fuel return line will cause a rich fuel condition.
White/Gray Smoke: White exhaust smoke is an indication that coolant is burning in the combustion chamber. These are possible causes:
Cylinder Head: A crack in the cylinder head (around the coolant jacket) will cause coolant to enter the combustion chamber.
Engine Block: A crack in the deck of an engine block near the coolant jacket will cause coolant to enter the combustion chamber.
Head Gasket: A damaged or blown head gasket will cause coolant to enter the combustion chamber resulting in white/gray smoke coming from the tailpipe.