I bought a second hand Isuzu KB250, While driving it will loose power and give a sound like KRRRRRR, after some few minutes or seconds it will release a smoke and picks up power as normal. I took it to a diesel mechanic where they said something about fuel pump. They claim to have fixed it. However the car currently does not have enough power and the only time you can feel it is real moving its when you get to 140km/h speed otherwise it is very low on speed.