A method detects a “misfire” condition in an internal-combustion engine including a control unit, a driving shaft and phonic wheel that is splined to the shaft and coupled to a sensor. The method comprises steps of: detecting intensity of a signal generated by passage of teeth of the 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.