Two problems related to ignition have been reported for the 1999 Ford E-150. The most recently reported issues are listed below.
Spark plug ejected from cylinder head of my 1999 Ford E-150 5. 4l engine. The threads were stripped and the dealer says $4000+ total repair. The fuel and air leaking into the engine compartment with a convenient ignition source, the spark plug, fortunately did not lead to a fire but it's potentially enormous. After internet searching, this seems to be a very common problem. Although the Ford dealer does not acknowledge this.
Windshield wipers go on by themselves. Odometer light flickers on & off. Problem has been ongoing since I purchased the vehicle in 2001.