My Astra feels low on power, it struggles to accelerate, and there's a lot more black smoke coming out of the rear than usual - visible smoke at constant speed and proper thick heavy black clouds when accelerating hard. Fuel economy has gone down noticeably.
Whatshould I check? Air mass flow sensor? EGR valve blocked? Fuel pump and/or injectors?
I've tried fuel additives of different brands but they haven't helped.
The last problem I had with the engine was a bad crankshaft speed sensor and it was replaced, after that there's been no fault codes or EML.
(The engine does have some oil in the coolant, but that a different kind of problem and wouldn't create black smoke... or would it??)
Thanks in advance for your replies.