Engine Belts And Pulleys problems of the 2003 Lincoln Town Car

I was driving from florida to south dakota and started up the first foothill of the ozark mountains about 35 miles west of jonesboro, arkansas on us 63. The cruise control had just started to increase the engine rpms when I heard a bang followed by what I thought was a belt or something thumping on the inside of the hood. Fortunately there was the 2nd entrance to a rest stop on us 63 immediately to my left and I pulled into the parking lot. Us 63 is a 2 lane highway with an occasional passing lane on some hills. It was also fortunate it happened at that point or I would have been in a difficult and dangerous position with little room to get safely off the highway with the narrow shoulders and rock cuts right up to the road. I opened the hood and restarted the engine in the parking lot. It was then I found something exploding on the passenger side of the engine. I could smell a lot of gas and shut the engine off immediately. I called aaa and was carried back to jonesboro on a flatbed about 3 hours later. I went to cavenaugh Ford the next morning and the problem was diagnosed as a spark plug blown out of the #3 cylinder. The repair with a full set of new plugs installed in addition to the bad cylinder cost $629 plus an additional $190 for towing. One additional plug on the driver side of the engine was also loose and a potential blowout. These plugs were factory original and have not been changed since the car was new. The mechanic told me the plugs were not properly torqued in at the factory which results in loosening of the threads in the head over time from the percussion in each cylinder. This appears to happen quite often on the 4. 6 and 5. 4 liter engines. I was lucky since many fires have also occurred because of these plugs blowing out of the engine.