There may be an extended warranty on the ignition coils - see your Ford Dealer for more information-Thanks John B for this information!
2003 Ford Thunderbird Problem Reports
Most Reported 2003 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.
The composite (plastic) intake manifold may crack near the thermostat housing and cause a coolant leak. Ford released an updated manifold that was reinforced to prevent a recurrence. No recall was issued for this problem but Ford did extend the warranty to seven years on some models from the date of purchase.
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.