Ford focus 1.5 diesel powershift wired noise.

[Remon23]

Hi everyone, I am based in Newcastle upon Tyne, this my first Ford car after always owning German cars , anyway 3 weeks ago I bought 66 plate 1.5 diesel focus estate powershift privately on gumtree, the car done 126k, car was driving fine but I noticed last 2 days the car idling rough, I opened the oil cap while idle and I can hear kind of a popping crackling noise coming from inside the engine, secondly when I try to rev it ever so slightly it feel like it juddering doesn't make a difference if it is idle or moving from a stop there is a bit of judder at a very low RPM, can anyone relate to that or have any idea?

Thanks