Patent ID: 6550318
Filing Date: 2003-04-22
Classification: F02D,F02M

Abstract:
An abnormality diagnosis apparatus for performing a leak check and for determining whether or not a leak exists in an evaporative fuel processing system which includes a fuel tank, a canister for storing evaporative fuel generated in said fuel tank, a charging passage for connecting said fuel tank to said canister, a purging passage for connecting said canister to an intake system of an internal combustion engine, and a purge control valve provided in said purging passage, said abnormality diagnosis apparatus comprising:a pressure sensor for detecting a pressure in said evaporative fuel processing system; pressure reduction processing means for executing a process of reducing the pressure in said evaporative fuel processing system with a limited flow rate of gases passing through said purge control valve when performing the leak check in an idling condition of said engine, wherein said limited flow rate being set to a value equal to or smaller than a predetermined flow rate which is smaller than the maximum flow rate applied to the leak check performed in operating conditions of said engine other than the idling condition; and leak determining means for performing the leak check on the basis of a change in the pressure in said evaporative fuel processing system after the pressure reduction process.