<div class="htmlview paragraph">The paper deals with the implementation of a diagnosis procedure able to reveal if anomalies in the combustion process of a spark ignition engine appear and then to identify the responsible cylinder.</div> <div class="htmlview paragraph">The procedure, based on the processing of the exhaust pressure signal in both time and frequency domains, has been developed aimed at overcoming the lacks others diagnostic methodologies have exhibited when the malfunction appears during some particular engine operative conditions.</div> <div class="htmlview paragraph">At first, the effectiveness of the method has been shown by considering steady-state conditions: experimental measurements have been carried out on a spark ignition engine running in a test cell by fixing different conditions of engine speed and load.</div> <div class="htmlview paragraph">In this paper the attention has been devoted to steady conditions in which the engine operating is characterized by a large amount of irregularity; engine transient conditions have been analysed, too.</div> <div class="htmlview paragraph">The results of both steady and transient tests are presented.</div>