Method of identifying a faulty fuel injector in an internal combustion engine

A method of identifying a faulty fuel injector in an i.c. engine having a plurality of fuel injectors, comprises (i) commanding in sequence each injector to inject a fuel quantity; (ii) measuring, during the combustion of the injected fuel quantities, a plurality of values of crankshaft speed; (iii) processing the measured values of the crankshaft speed to calculate, for each injector, a respective unbalancing value representative of the fuel quantity injected by the injector (block 510); (iv) calculating an average value of the calculated unbalancing values (520); (v) subtracting the calculated average value from each of the unbalancing values to obtain, for each injector, a respective adjusted unbalancing value (530); (vi) calculating the standard deviation of the adjusted unbalancing values (540); (vii) multiplying each of the adjusted unbalancing values by the standard deviation to obtain, for each injector, a respective corrected unbalancing value (550); (viii) comparing each of the corrected unbalancing values with a predetermined threshold value thereof (560); and (ix) identifying a faulty injector if the corresponding corrected unbalancing value exceeds the predetermined threshold value (570).