1. A method for detecting a misfire condition in an internal-combustion engine that includes a control unit, a driving shaft and phonic wheel that is splined to the driving shaft and coupled to a sensor, the method comprising steps of: detecting intensity of a signal generated by passage of teeth of the phonic wheel by the sensor; sampling the signal generated by the passage of the teeth; processing the sampled signal by applying a discrete Fourier transform; representing the sampled signal processed by a virtual phasor that represents in a vector form the signal that has been sampled and processed; determining a corresponding theoretical phasor for the virtual phasor that represents theoretical evolution of the signal that has been sampled and processed over time; comparing the theoretical phasor with the virtual phasor; and determining presence of a misfire condition by comparing the theoretical phasor with the virtual phasor that represents the signal that has been sampled and processed; and detecting the presence of the misfire condition according to an increase in amplitude of the signal that has been sampled and processed.