l have a 97 manual Hyundai excel, and all of a sudden it has started jerking really bad, only when l accelerate though not when shifting down in my gears. l have no clue what it is, as when l first go the car it was jerking a little bit but not much, so l got the spark plugs replaced, and it has driven perfectly until now, but its jerking really bad atm, what could it be ? l changed the spark plugs not long ago, do u think they may need to be replaced again?
How often should you change spark plugs? please help =[

could be a bad spark plug wire.

If it only happens on hard acceleration and not as bad on mild accel, inspect your air intake hose from the air cleaner to the intake manifold. l have found that they tend to crack, making the vehicle jerk violently under acceleration.

Electrical