Abstract: It is known that the performance of actual fuel injectors tends to deviate from performance of nominal fuel injectors in both quantity and timing of each fuel injection event. These deviations in timing and/or quantity can be a function of such variables as the on-time itself, rail pressure in the case of hydraulically actuated fuel injectors, and engine temperature. In addition, these variations in performance can change over the life of the fuel injector. Therefore, in order to accurately correct for performance deviations in each individual fuel injector, the invention can include an up-to-date diagnostic of that deviation in performance. The present invention includes in-chassis strategies for evaluating fuel injector performance deviations in both quantity and timing, and further includes software strategies for applying control signal adjustments to make all of the fuel injectors in a given engine behave more uniformly and more like a nominal fuel injector.