Two stage monitoring of evaporative purge system

摘要

An evaporative purge system 10 of an internal combustion engine 14 powered motor vehicle is monitored using one or more relatively long time tests in the cruise operating mode of the motor vehicle to screen for emission of vapors which, allegedly, contributes to smog. If emission is detected in the cruise operating mode, a command is generated and stored in memory to subsequently monitor the system in the idle operating mode. The evaporative purge system is subsequently monitored using a relatively short time test in the idle operating mode of the motor vehicle to confirm vapor emission.