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Originally Posted by Drjsuh
Very informative. I had heard of similar issues with audi direct injection cars. Does anyone know if the diesel bmw's have the same issues since they are direct injection too?
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All pure DI engines have this issue - oil vapors from the crank case ventilation system are piped into the motor's intake and ingested by the motor. On a non-DI car, fuel is injected above the intake valves, constantly cleaning them. On a DI car, fuel is injected directly into the cylinder, behind the intake valves so they're not cleaned.
Toyota uses a hybrid DI/port injection system where fuel is delivered by both mechanisms - the fuel injected into the intake port cleans the valves and prevents this problem. Interesting enough - that system was not designed to fix this issue but rather to address the fuel delivery problems at high RPM operation they had with older injectors. The clean valves were a welcome unintended side-effect.