Wide range control method for a fuel vapor purge valve

A method of operation for an internal combustion engine having a fuel control for maintaining an air/fuel ratio of said engine at a desired value, and a fuel vapor purge system including a purge valve that is electrically activated at a variable level to define an effective opening corresponding to such activation level through which stored fuel vapor is purged into said engine, said purge valve having a nominal minimum activation level for reliably defining a corresponding minimum effective opening, the method comprising the steps of:

• estimating a percentage of engine fuel supplied by said purged fuel vapor;
• initiating a low flow control of said purge valve when the estimated percentage exceeds a calibrated value and the activation level of the purge valve has been reduced to said nominal minimum level;
• and
• when said low flow control is initiated, progressively reducing said activation level below said nominal minimum level to define effective openings of said valve that are smaller than said minimum effective opening so long as the air/fuel ratio of said engine is within a calibrated amount of said desired value.