Engine fire fault diagnosis method

Abstract

The invention provides an engine fire fault diagnosis method, which comprises the following steps of: judging whether an engine has an influence on a fire diagnosis fault, updating the information index value of the fire diagnosis fault, judging whether the engine satisfies the operating condition of engine fault diagnosis, judging whether the current working condition is in an area of prohibiting fire diagnosis, determining a fire cylinder according to the acceleration characteristic value in an acceleration mode, calculating a torque characteristic value in a torque mode, judging whether a catalyst damage type fire exists according to the fire rate, and judging whether emission degradation type fire exits according to the fire rate. By the method, the fire of the engine can be timely and accurately discovered, the accuracy of the fire diagnosis is improved, erroneous judgment is avoided, and the fire caused by emission damage or catalytic converter damage can be determined.

Description

technical field [0001] The invention relates to an engine misfire fault diagnosis method, in particular to a misfire fault diagnosis method used in an on-board diagnosis (OBD) system. Background technique [0002] The OBD system is very important for the fault diagnosis of engine misfire. When the engine misfires, a large amount of unburned combustible mixture enters the catalytic converter, resulting in excessive emissions. At the same time, unburned HC (hydrocarbons) and a large amount of oxygen will be in the Combustion in the catalytic converter will cause the temperature of the catalytic converter to rise, resulting in rapid damage to the catalytic converter. Therefore, OBD must be able to detect any misfire, single-cylinder misfire or multi-cylinder misfire that causes a sudden change in HC emissions. The misfire diagnosis must not only detect the misfire phenomenon, but also determine whether the engine misfire is an exhaust-damaged misfire or a catalytic converter-da...

AI Technical Summary

Problems solved by technology

Although the calculation is simple by using the torque mode or the acceleration mode alone, it is easy to cause inaccurate measurement results and misjudgment when the vehicle is at a high speed stage or on a bad road.

Images