Focus MK2.5 TDCI 1.6 black smoke under heavy acceleration

Hi all,

Looking for a bit of advice on a 2009 Focus MK2.5 1.6 TDCi.

The car produces black smoke under heavy acceleration/load when lifting off the accelerator afterwards, but otherwise it drives fairly normally. The strange part is that the smoke disappears completely when the MAF sensor is unplugged.

The black smoke issue itself has only been present for about the last month, maybe longer and I hadn't noticed. Before that, the car had noticeable flat spots/hesitation in certain parts of the rev range, but interestingly those have also completely disappeared since disconnecting the MAF sensor.

I’ve already replaced the MAF with a brand new Bosch unit, but it made no difference. The car actually runs fairly well with the MAF unplugged, although it feels slightly more sluggish and possibly uses a bit more fuel.

I’ve done quite a bit of diagnosis using FORScan and live data logging. Rail pressure appears healthy both at idle and under load, around 250 bar at idle and climbing to roughly 1400 bar under acceleration. RPM, MAP, turbo control (VGTDC), accelerator pedal and MAF readings all appear to respond normally during live logging.

So far I’ve also:

• cleaned the MAP sensor

• cleaned the EGR valve

• checked for intake/boost leaks using carb cleaner

Has anyone seen similar symptoms on the 1.6 TDCi?

Edited May 20May 20 by LiamKD