Crankcase Ventilation Issue

The symptoms you describe sound indicative of a crankcase ventilation malfunction. The reduced power and smoke are concerning. Is the smoke dark or more of a bluish hue? Have you noticed any unusual oil consumption lately? A faulty valve can cause pressure issues within the engine, leading to leaks and improper combustion. These engines are quite sensitive to ventilation problems.

The smoke is more bluish, and yes, I think I've been topping up the oil more frequently than usual. What exactly happens when this valve fails? Is it something I could potentially fix myself, or am I looking at a workshop visit?

Ah, bluish smoke and increased oil consumption strengthen the diagnosis. A defective crankcase ventilation valve disrupts the proper evacuation of crankcase gases. This can lead to pressure buildup, forcing oil past the piston rings and valve seals, hence the blue smoke. While a technically inclined individual might attempt a DIY replacement, I must recommend entrusting this repair to a qualified workshop. Incorrect installation or diagnosis could exacerbate the issue, potentially leading to more costly repairs. Proper diagnostic tools are also essential to confirm the fault. The repair will probably cost around 360€.

Thanks a lot for the detailed explanation. I suspected it was a job for the professionals. I'll book it in at a local shop this week. It seems that the crankcase ventilation was indeed the issue, I got the car back and it runs as new.