Abstract: A control scheme is disclosed for performing both an adaption routine and carbon canister purging. In adaption, parameters for estimating air-fuel ratio from flow sensors and actuators are adjusted against an air-fuel ratio under closed-loop control using an EGO sensor. The two processes cannot run simultaneously. In vehicles in which the engine is operating from the time of key on until key off, the adaption occurs shortly after starting and then periodically thereafter. In vehicles in which the engine is turned on and off frequently such as with HEVs, the adaption routine may be run every time the engine is turned on, which is more frequent than necessary and doesn't allow enough time for purging. According to the disclosed control scheme, the time since last adaption and time in adaption is saved when the engine is turned off so that the adaption routine is conducted only when needed.