A spark ignition type engine enabling engine startability to be favorable is provided. The spark ignition type engine includes a main intake-air passage; a throttle valve of the main intake-air passage; a bypass intake-air passage bypassing the throttle valve; an ISC valve of the bypass intake-air passage; and an electronic control device that controls an engine speed by adjusting an opening degree of the ISC valve, in which when the engine is started, cranking is performed at a cranking opening degree at which the ISC valve is narrowed by a predetermined amount from a fully opened state by control of the electronic control device, so that an intake-air negative pressure is generated on an intake-air downstream side of the ISC valve.

A spark ignition type engine enabling engine startability to be favorable is provided. The spark ignition type engine includes a main intake-air passage; a throttle valve of the main intake-air passage; a bypass intake-air passage bypassing the throttle valve; an ISC valve of the bypass intake-air passage; and an electronic control device that controls an engine speed by adjusting an opening degree of the ISC valve, in which when the engine is started, cranking is performed at a cranking opening degree at which the ISC valve is narrowed by a predetermined amount from a fully opened state by control of the electronic control device, so that an intake-air negative pressure is generated on an intake-air downstream side of the ISC valve.

A method of conducting prognosis for an airflow management system for a combustion engine includes adjusting a throttle body valve position control signal in response to a detected airflow variation and monitoring an airflow variation compensation (AVC) value corresponding to a degree of adjustment of the control signal. The method also includes generating a throttle body coking severity metric based on at least a plurality of residual error values and the AVC value, and executing at least one response action based on the throttle body coking severity metric exceeding a predetermined threshold.

Methods and systems are provided for an internal combustion engine having at least two cylinders configured in such a way that they form two groups, at least one cylinder of a first group being a cylinder which is operational in the event of a partial deactivation of the engine, and at least one cylinder of a second group being formed as a load-dependently switchable cylinder. An inlet-side throttle element is provided with at least one intake line of the switchable cylinder, by means of which the size of the flow cross section of the intake line can be varied, whereby the charge-air flow rate supplied to the deactivated cylinder in the event of a partial deactivation of the engine can be adjusted. Each outlet opening of a load-dependently switchable cylinder is equipped with a partially variable valve drive, with an outlet valve which opens or shuts off the outlet opening.