My 1.9l diesel punto, which I purchased a week ago has an annoying problem, iat low revs in 3Rd and 4th it kinda does this jerking/jolting pogoing thing. I've noticed air/fuel leaking from under the big nut at the base of the injector, and this is all I can see is wrong, would this cause the car to do this? And if so how do I fix it. Cheers in advance