Vios jerking when accelerating

[17Sphynx17]

Sorry sir 1.3J Manual po Vios ko

Is it only between 70 to 80kph? If you go higher than 80kph, does it disappear? If you go higher than 80, are you shifting to the highest gear? On 70 to 80kph, did you just shift into the new gear or was it specifically just to do with the speed? Meaning say if you stuck with 4th gear and floored it to climb to 70-80kph range, does it still experience jerking, same when you do that speed when on 5th gear?

You might be seeing my train of thought here. I am wondering if it is less to do with the engine, and more to do with the transmission slipping, maybe. I am not sure. I'm just hazarding a guess. Because the speed you mentioned is too specific. If it were based on the engine, i would expect it to present within an rpm range, instead of a speed range.