Lincoln town car signature series rough idle and check engine light flashes for a while than goes to a steady light

A flashing check engine light means there is an active misfire. Stop driving the vehicle until you resolve this, or you may cause significant further damage...if you have not already. Could be as simple as replacing the spark plugs and coils or at least coil boots with Ford original equipment parts. Hands on testing is needed for this and the other shared concerns. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops