Investigators say at about 12:15 in the morning, a gunman walked up to a cabbie at the Sunoco gas station at Broad and Windrim streets in the Logan section of the city.
He forced the cabbie to hand over his Germantown cab, a black Ford Crown Victoria.
The suspect then jumped into the cab and drove south on York Road.
About three hours later officers found the vehicle on the 2000 block of Tulpehocken Street.The suspect was not inside and remains on the loose.
The cab driver was not injured.