Methods and system for central fuel injection

An engine system, comprising:

• an engine intake manifold including a manifold air temperature sensor;
• a plurality of engine cylinders;
• one or more direct injectors configured to direct inject a fuel into one or more of the plurality of cylinders;
• one or more port injectors configured to port inject the fuel into one or more of the plurality of cylinders;
• a central fuel injector to inject the fuel into the engine intake manifold;
• an engine exhaust manifold including an exhaust passage, an exhaust catalyst coupled to the exhaust passage, and an exhaust oxygen sensor coupled to the exhaust passage upstream of the exhaust catalyst;
• and
• a controller with computer-readable instructions stored on non-transitory memory for:
• in response to one of a higher than threshold oxygen content in the exhaust catalyst and a higher than threshold engine intake manifold temperature, selectively increasing a ratio of fuel delivered via the central fuel injector relative to fuel delivered via each of the direct injectors and the port injectors, the oxygen content estimated via the exhaust oxygen sensor and the engine intake manifold temperature via the manifold air temperature sensor.