I try to explain it once again. Start is fine. Will give a litle jerk when apply 2nd gear. When you turn to 3rd and 4th gear at a speed around 70-80, suddenly there are very bad jerks, car jolts like fuel has ended. Then lower the gear or free the accerator for a while and push again then the car will run fine but for some time only (at a speed 100 to 120 there is no problem at all or drive it in 3rd gear up to 90-100 then ther's no probelm).
Its also happens when traveling to some higher place on an even road. Like when I travel to murree this seen(jerks/missing) is continous on the whole road until i convert to petrol.