COMBUSTION STATE DIAGNOSTIC DEVICE FOR INTERNAL COMBUSTION ENGINE

PURPOSE:To improve the detecting accuracy in a device for detecting the combustion state of an engine from fluctuations of the engine speed by correcting combustion state parameters, etc., containing error factors based on information on the engine speed in a specific operating condition, and information on abnormality in combustion by an air-fuel ratio sensor, etc. CONSTITUTION:In response to the combustion process of an internal combustion engine, the time required to rotating through a specified crank angle is measured by a calculating means 701. Based on the specified time, combustion state parameters are calculated by a calculating means 702. Then, the calculated combustion state parameters are inputted to a correcting means 703. On the other hand, the output of an air-fuel ratio sensor is detected by a detecting means 704 to be A/D converted, and the information on the combustion state detected by a judging means 705 is inputted to the correcting means 703. Then, the correcting means 703 corrects errors of the width of the engine speed measuring range, messes of operating members, etc. Thereafter, a judging means 707 judges the combustion state in response to the corrected combustion state parameters, and at an abnormal time, an informing means 708 informs the abnormality.