Final answer:
The least likely cause of excessive blue smoke in the exhaust of a turbocharged engine is a PCV valve stuck in the open position. The most likely causes are worn turbocharger seals, worn valve guide seals, or worn piston rings.
Step-by-step explanation:
The LEAST LIKELY cause of excessive blue smoke in the exhaust of a turbocharged engine is a PCV valve stuck in the open position. The PCV (Positive Crankcase Ventilation) valve is responsible for removing blow-by gases from the engine crankcase and sending them back into the intake manifold to be burned. If the PCV valve is stuck open, it can cause excessive oil consumption but not necessarily blue smoke in the exhaust. Blue smoke is usually a result of burning oil.
The most likely causes of excessive blue smoke in the exhaust of a turbocharged engine are worn turbocharger seals, worn valve guide seals, or worn piston rings. When these components wear out, engine oil can enter the combustion chamber and burn along with fuel, causing the blue smoke.