Abstract: A method and apparatus for identifying a faulty fuel injector is disclosed. The fuel injectors are commanded in sequence to inject a fuel quantity. A plurality of values of a crankshaft rotational speed is measured during the combustion of the injected the quantities. The measured values are processed to calculate a respective unbalancing value representative of the fuel quantity injected by the fuel injector. An average value of the calculated unbalancing values is calculated and subtracted from each of the unbalancing values to obtain a respective adjusted unbalancing value. The standard deviation of the adjusted unbalancing values is calculated and multiplied with each of the adjusted unbalancing values to obtain a respective corrected unbalancing value. The corrected unbalancing values are compared with a predetermined threshold value thereof, and a faulty fuel injector is identified if the corresponding corrected unbalancing value exceeds the predetermined threshold value.