Failure Fire 1.3

Good morning friends .. I have a failed faultly annoying in my Fiat Palio is the sink. If I hold the accelerator in 1500 rpm the vehicle goes out both ascending and unpaying but only if the accelerator remains in those rpm for a couple of seconds .. In a tail imagine the number of times that goes out .. I have managed to control that keeping it on those rpm ... I fail to find the failure according to I believe is the potentiometer of the accelerator pedal! What do they tell me?