Hello, repair your ignition lock cylinder properly. Obtain proper keys for the vehicle. Have them programmed to your vehicle.
Use this link to find some shops near you that can help with your concern:
www.repairpal.com/repair-shops
RepairPal Certified shops can diagnose and repair your 2004 Mercury Grand Marquis. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.