b180 cdi low revv problem

Hi All, I own a 2006 B180 cdi, W245.207, manual gearbox with about 200,000kms. There is an ongoing problem where the car starts to misfire and jump at low revs from about 1,400rpms to 2,000rpms in any gear. Once it passes 2,000rpm the car accelerates normally all the way to the red line. There...