Abstract: In accordance with an exemplary embodiment, a method is provided for controlling operation of an engine of a vehicle during an idle mode of operation for the engine, the engine having a plurality of different types of fuel injectors and a combustion chamber, including: obtaining, via one or more first sensors of the vehicle, first sensor data as to a speed of the vehicle; obtaining, via one or more second sensors of the vehicle, second sensor data as to a measure of roughness of the engine; and adjusting, via instructions provided by a processor of the vehicle, a fuel injection ratio of respective amounts of fuel provided by the plurality of different types of fuel injectors to the combustion chamber, based on both the speed of the vehicle and the measure of roughness of the engine.