A number of motoring forums seem to be catching on to problems with recirculation of crankcase gasses into the inlet manifold to be burnt as part of the combustion process.

It would seem the blowby gasses pick up oil vapour thus coating the various sensors, hoses etc.

This seems to be more of a problem with direct injection engines - like those on modern Audis. The lack of fuel vapour into the inlet manifold means that a lot of the oil deposits are not washed away.

It all beggars the question, why dont manufacturers build a filter into the system to catch the oil vapour?

It seems most older cars seem to eventually suffer from rough idling due to blocked sensors, stepper motors, gunged injectors. Engines with direct injection now seem to be suffering from excessive carbon buildup on the valves etc. Perhaps a return to the old days of a de-coke every few thousand miles.

Any thoughts?