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.Google+
Car Problem Reports
Ford Thunderbird Check Engine Light Due to Oil Leak in Valve Cover Gasket
Ford Thunderbird Problem
Engine Affected: 4.6L V8
Average Mileage: 77,114 mi (35,000 mi - 175,000 mi)
replace coils frequently
Visitor, 2002 Ford Thunderbird, 72,000 mi
Car idle choppy. Check engine light came on. Problem waS leaking gasket filled spark plug wells with oil. Causing arc. Costing 1,100. Ouch
Visitor, 2003 Ford Thunderbird, 56,000 mi
replaced 4 cop's over 3 yrs
Oil in spark plug wells. Cleaned and checked plugs, wells, and coils. Will have to replace Valve Cover Garkets at some point. Running well for now.
Dealer told me that there was moisture (water) under coil covers and that I needed new retro-fitted coil covers and seal by wiper motor @ a cost of $475.00.
Checked it myself, no moisture but oil in wells. Took 2 1/2 hours to clean and replace coil covers. Now I have to replace Valve Cover Gaskets next.
3 plugs misfiring, found that oil leaking into spark plug wells, expensive $1200 repair. Car is always garaged, driven less than 5,000 miles a year, and serviced regularly. Not happy.
Visitor, 2005 Ford Thunderbird, 110,000 mi
oil in spark plug wells, causes random misfires.
Not fixed yet, 8 plugs misfiring, you can figure out the rest:(
Visitor, 2002 Ford Thunderbird, 76,500 mi
misfiring engine, engine light came on. Took it in for diagnostic and found #1 spark and ignition coil defective due to water in spark plug, cost of repair, $459.00. Same thing happened 5 months later with the #3 plug and coil. Definately a poor design by Ford... Now the engine is doing an occasional miss and I'm sure another coil and plug are to blame....
Visitor, 2002 Ford Thunderbird, 47,000 mi
Misfire, rough idle and driving. Oil leak into valves due to valve cover gasket failure. Replace coils and gaskets. $1200. This is apparently a known (too well) issue with 2002 Ford Thunderbirds, warping valve covers due to engine heat also leads to the leaks.