Abstract: The present invention has an object to effectively prevent deterioration of combustion characteristics when engine temperature is low. There is provided an intake pressure controller 24 that effects control such that, when an operating condition discriminator 21 that identifies engine temperature identifies low engine temperature after engine start-up, control by an engine controller (feedback controller 23) that performs engine control on fluctuation of intake negative pressure to decrease the intake negative pressure is suppressed until the temperature of the intake passage rises to at or above a predetermined value, and such that the intake negative pressure is made larger.

Abstract: The present invention has an object to effectively prevent deterioration of combustion characteristics when engine temperature is low. There is provided an intake pressure controller 24 that effects control such that, when an operating condition discriminator 21 that identifies engine temperature identifies low engine temperature after engine start-up, control by an engine controller (feedback controller 23) that performs engine control on fluctuation of intake negative pressure to decrease the intake negative pressure is suppressed until the temperature of the intake passage rises to at or above a predetermined value, and such that the intake negative pressure is made larger.

Abstract: An engine control system for controlling combustion of an internal combustion engine equipped with an exhaust gas purifying catalyst. The system controls fuel combustion on the basis of control parameters including air/fuel ratio, ignition timing and intake air flow so as to cause a rise in exhaust gas temperature while an exhaust gas purifying catalyst installed in an exhaust line of the engine is insufficiently warmed or inactive. When a fluctuation of engine speed is detected, the system controls the air/fuel ratio to reach a target value close to a stoichiometric value, for example, a value between 13 and 17, and controls a control parameter other than air/fuel ratio so as to bring the fluctuation of engine speed within limits of stable combustion while the exhaust gas purifying catalyst is insufficiently warmed. The air/fuel ratio feedback control may be commenced immediately after an engine start.

Abstract: A fuel combustion control system for an internal combustion engine having an exhaust gas purifying catalyst installed in an exhaust line therein advances an ignition timing to try to stabilize combustion when a fluctuation of engine speed is larger than a limit speed on stable combustion and further retards an ignition timing to accelerate a rise in catalyst temperature together with securing combustion stability while the engine is still cold or when a fluctuation of engine speed is smaller than the limit speed on stable combustion.

Abstract: An engine control device has an idle speed control of an engine by an ignition timing control and an idle speed control by air-by-fuel ratio feedback. This engine control device detects roughness caused by a torque change on the basis of a change in angular velocity of a crank shaft, sets a control gain depending on the roughness, reflects the control gain on the idle speed control by the ignition timing control, thereby harmonizing the idle speed control of the engine by the ignition timing control with the idle speed control by the air-by-fuel ratio feedback.