Hi guys,
First of all I'd like to thanks for kind suggestions.

After getting all your suggestion I had open engine head and found all valves are worn out. I installed the engine head after repairing but there is quite improvement which is engine is running smoothly when I'm not using any other function. I have observed following issues.

1. When using any hydraulic function (Lift, tilt up, side shift & steering).
Engine speed will increase before reaching the end position but at the end of position engine will suddenly goes off.
2. When drive.
Truck driving speed is smooth but when we completely press any pedal (reverse, forward) truck drives with jerk.