330i (N52) issues: black smoke, reduced performance - HELP!
This relates to my 2007/57 pre-facelift N52 330i.
Last weekend (on the way home from hospital after the birth of my daughter, of all the bad times for it to happen...) I got a LOT of grey/black smoke from the exhaust under hard acceleration, with the smoke continuing after lifting off. Smoke also present on start up from cold and from warm. And we're talking a LOT of smoke: enough to totally obscure the car you've just overtaken . Oil level is fine, coolant level perfect, nothing untoward under the oil filler cap. Lots of black bits on the rear of the car (like the particles you'd get from a diesel) and exhaust itself is very black. Performance is reduced - just doesn't feel like full power, with the occasional stutter/misfire. I've tried a treatment of Redex injector cleaner but no difference.
This morning I took it to a recommended auto electrician/mechanic. No codes were brought up on the fault reader initially. Mechanic took it from a drive with me in the car - after hard acceleration off a roundabout his exact words were, "Oh ya f**ker* as he looked at the amount of smoke behind the car...
Got back to garage, disconnected the MAF sensor (aka air flow meter) and went for another drive: no smoke whatsoever and decent - although possibly not full - performance. Stopped in a layby, reconnected the MAF sensor, and as soon as we drove off an engine management light came on, smoke reappeared from the exhaust, and the car was incredibly hesitant and running poorly. Fault reader diagnosed a problem with combustion in cylinder 5, no other fault codes reported.
We're all a bit unsure where to start so looking for ideas/opinions...
It's definitely running rich - burning too much fuel.
Initially he's going to replace the MAF sensor for starters, but if that doesn't solve it does anyone have any good/sensible suggestions?
BMW e90 330i M Sport