Buddy, majority of this problem is faced in Santros and Balenos.About this specific problem, u can check by running the car in a higher gear while on very slow speed and then try pressing the accelerator, this is a way to check but from what I have found, the fault is with mechanics who do not know how to check a car, since there is always a reason why such happens, sadly in my case santro own ppl didnt know. Not to mention, i myself do not know so much about technicalities of cars, so i would leave your questions answer to someone else
I have used city, santro, corolla, mehran, khyber, cultus and somehow no matter what, if i had a choice, i would opt for honda.