There may be an extended warranty on the ignition coils - see your Ford Dealer for more information-Thanks John B for this information!
2005 Ford Thunderbird Problem Reports
Most Reported 2005 Ford Thunderbird Problem Reports
The valve cover gaskets may leak oil into the spark plug wells, shorting out the spark plugs, causing a misfire, and illuminating the Check Engine Light. Commonly the spark plugs and ignition coils or wires will require replacement, along with resealing the valve cover to correct this concern.
Water or oil may enter into the ignition coil cover and the spark plug bore, causing a misfire and illuminating the Check Engine Light. A coil with improved water and oil sealing is available and should be installed.