I'm having an issue with my 2009 Volkwagen Golf Plus 1.9 TDI. After driving the car between 20 - 40 minutes, there is a sudden loss of power, a lot of smoke, a burning smell and a crunching sound from the front. The car will then only rev to about 2000rpm and barely moves.

No faults show on the dashboard, the engine temperature never rises abnormally high and the oil level is normal and shows no signs of loss. Once the car has been switched off for between 5 - 20 minutes, it seems to drive normally again, although the engine before and after the problem feels ‘lumpy’. This has happened four times in four days. Any ideas on what could be causing this?