Abstract: When an insulation resistance value of an ignition plug is smaller than a prescribed value, an engine operation state is switched so as to raise a temperature of the ignition plug, thereby promoting deposit cleaning. Such a measures-against-deposit carrying-out state is counted. When a count value exceeds a certain value, that is, when the measures against deposit have sufficiently been performed but the insulation resistance value of the ignition plug is smaller than the prescribed value, it is determined that conductive deposit has adhered to the ignition plug, and for example, an alarm light is turned on in order to urge a driver to perform maintenance of the ignition plug.

Abstract: When an insulation resistance value of an ignition plug is smaller than a prescribed value, an engine operation state is switched so as to raise a temperature of the ignition plug, thereby promoting deposit cleaning. Such a measures-against-deposit carrying-out state is counted. When a count value exceeds a certain value, that is, when the measures against deposit have sufficiently been performed but the insulation resistance value of the ignition plug is smaller than the prescribed value, it is determined that conductive deposit has adhered to the ignition plug, and for example, an alarm light is turned on in order to urge a driver to perform maintenance of the ignition plug.

Abstract: A crank angle sensor outputs a pulse signal whenever a crankshaft rotates a predetermined angle. An ECU performs an elimination process on a sequence of pulse signals to obtain a remaining signal used to determine the crank angle. When the rotation speed of the crankshaft becomes lower than a predetermined threshold, the ECU suspends the elimination process and determines the crank angle using pulse signals that have not undergone the elimination process. The ECU detects reverse rotation of the crankshaft based on pulse signals that have not undergone the elimination process. A crank counter is operated in synchronism with the falling of a pulse signal when the crankshaft rotates in the forward direction and is operated in synchronism with the rising of a pulse signal when the crankshaft rotates in the reverse direction.

Abstract: A crank angle sensor outputs a pulse signal whenever a crankshaft rotates a predetermined angle. An ECU performs an elimination process on a sequence of pulse signals to obtain a remaining signal used to determine the crank angle. When the rotation speed of the crankshaft becomes lower than a predetermined threshold, the ECU suspends the elimination process and determines the crank angle using pulse signals that have not undergone the elimination process. The ECU detects reverse rotation of the crankshaft based on pulse signals that have not undergone the elimination process. A crank counter is operated in synchronism with the falling of a pulse signal when the crankshaft rotates in the forward direction and is operated in synchronism with the rising of a pulse signal when the crankshaft rotates in the reverse direction.

Abstract: The invention provides a preignition detection device that is capable of detecting a preignition condition (PI) in an incipient stage. Engine vibration is detected by a vibration sensor 113 and read into a controller 12. When the length of a period during which abnormal vibration of a magnitude greater than a predetermined level occurs in succession has exceeded a predetermined length of period, or when the frequency of occurrence of abnormal vibration during a predetermined period is greater than a predetermined value and the cumulative sum of the frequencies of occurrence of abnormal vibration has exceeded a predetermined value, then it is determined that preignition has occurred. Here, a determination value, based on which the occurrence of preignition is determined, can be varied to prevent erroneous decisions and to improve responsiveness.

Abstract: A preignition detecting system capable of detecting a preigniting condition (PI) at an early time. Vibration of an internal combustion engine is detected by a vibration sensor 113, and is fetched by a controller 12. The crank angle is detected by a crank angle sensor 111. It is so determined that PI has occurred when a difference between the ignition timing and the crank angle at which the vibration level exceeds a predetermined level becomes smaller than a predetermined value. It is further determined that the PI is occurring when the vibration level continues to increase despite the ignition timing being delayed continuously, enabling the occurrence of PI to be detected quickly and reliably. Furthermore, the constitution is simplified by installing a first gate that opens after the passage of a short period of time from the ignition timing and a second gate that opens thereafter.