| 摘要 |
PROBLEM TO BE SOLVED: To carry out a trouble diagnosis, even when some abnormality is generated in a variable valve timing control mechanism (VVT), and it is fixed at the middle position of the most timing advance side and the most lag side. SOLUTION: The combustion condition of an internal combustion engine 1 is not stable, when either one of the ISC opening of an ISC valve 5, the ingnition timing by an ignitor 8, or the rotary variation amount of the engine rotation frequency by a crank angle sensor 13, is not less than a specific value, even though the internal combustion engine 1 is in an idling operation time. As a result, it is decided that the actual timing advance value cannot follow and is not near the most lag side, even though the target timing advance value as the controlled variable to the VVT 11 is the most lag side, and the valve overlap is large. Consequently, even though an abnormal condition is generated to the VVT 11 from some cause, and a trouble to fix the VVT 11 at the middle position between the most timing advance side and the most lag side is generated, it can be decided accurately.
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