115tdi Miss under load

[nokiamutt]

I have a 115 tdi ,has never missed a beat until recently when under load from as low as 1200 rpm (foot flat on the floor) to 2000rpm the car seem like a big missfire or a constant judder ,as if it has too much power ! but once its out of that rev range it just flies , i just have no ideas where to start , any advice would be great .
Cheers
Alan

[zollaf]

you need a fault code read.