can be appreciated that the engine 18 can include more or fewer cylinders 28 including but not limited to 1 3 4 5 6 8 10 and 12 cylinders the fuel injection system 20 includes liquid injectors that inject liquid into the cylinders 28 exhaust flows through the exhaust manifold 24 and is treated in a catalytic converter 30 first and second exhaust oxygen sensors 32 and 34 e g wide range a f ratio sensors communicate exhaust a f ratio signals to the control module 16 a mass air flow maf sensor 36 is located within an air inlet and communicates to the control module 16 a maf signal based on the mass of air flowing into the engine system 12 an engine speed sensor 38 senses the speed of the engine and communicates an engine speed signal to the control module 16 a throttle position sensor 40 senses the position of the throttle 26 and communicates a throttle position signal to the control module 16 the control module 16 controls the fuel and air provided to the engine based on oxygen sensor signals and throttle valve position this form of fuel control is also referred to as closed loop fuel control closed loop fuel control is used to maintain the air fuel mixture at or close to an ideal stoichiometric air fuel ratio by commanding a desired fuel delivery to match the airflow stoichiometry is defined as an ideal air fuel ratio which is 14 7 to 1 for gasoline the engine control may command different airflow to compensate the engine speed changes during engine idle operation the engine system 12 operates in a lean condition i e reduced fuel when the a f ratio is higher than a.