Black smoke plus power loss on a Q3 II TDI usually means too much fuel and not enough clean air.
Here are the likely causes, what to check first, and when to stop driving.
Feeling your Q3 II go flat the moment you ask for real acceleration is frustrating — and when a dark haze appears in the mirror at the same time, the car is telling you something specific. Black smoke is unburnt fuel: the engine is getting more diesel than it can burn, almost always because the air side is restricted or the turbo is not building the boost it should. On the 2.0 TDI (35 and 40 TDI) that narrows things down to a handful of usual suspects, and yes — EGR and DPF clogging are right at the top of the list.
