When I replaced the spark plugs I torqued the plugs properly and it ran great for about 5,000 miles until the #6 cylinder spark plug blew out and ruined the Coil-On-Plug along with it. The thread inside the spark plug well was ruined and I ended up taking it to a local mechanic. The mechanic used a time-sert kit to re-thread it and replaced all the plugs with factory plugs since he says that's a more permanent fix and should not happen again.

So moral of the story is to use the factory plugs, the problem I think is that I used aftermarket plugs.

Replaced left cylinder head, as #7 spark plug threads were gone and spark plug ejected. Repaired 04/03/2006 for $50.00.

This is one of two consecutively VIN-numbered 2003 Ford Crown Victoria NGV P73 vehicles ordered from the factory that had this problem. Both cars had extended warranties purchased, however only this green-colored vehicle's [VIN 2FDFP73943X207899] extended warranty was in force when the spark plug ejected from the cylinder head at 64,380 miles.

In a separate complaint the other 2003 Ford Crown Victoria NGV P73 vehicle, white-colored [VIN 2FDFP73923X207898] had spark plug ejection on 12/19/2006 at 83,148 miles was off warranty and out of service until 03/29/2007. Repair cost $5,704.89 included unrelated early change of timing belt.

This was the second incident for this 2003 Ford Crown Victoria Natural Gas Vehicle, VIN...898. In first incident spark plug #2 blew out on 09/05/06 at 75,632 miles. One Ford dealer made repair after expiration of extended 75K warranty at cost of $671.26 using a spark plug insert kit, and completed repairs on 09/05/06. The second incident involved a spark plug ejected from other cylinder head on 12/19/06 at 83,148 miles. A different Ford dealer repaired by replacing both cylinder heads (and timing chain, early) at cost of $5,704.89. Problems in obtaining correct cylinder heads at dealership delayed completion of repairs until 03/30/07. Ford technician's "diagnose and advise" note reports cause as "incorrect heads."

Also, had two incidents of spark plug ejection from another 2003 Ford Crown Victoria Natural Gas Vehicle, VIN...899. First incident spark plug #7 ejected from left cylinder head on 03/27/06 at 64,380 miles. Extended warranty covered all but $50 of the cost of replacing the left cylinder head. That repair was completed on 04/03/06. In the second incident spark plug #4 ejected from the right side cylinder head on 08/01/06 at 72,177 miles. A different Ford dealer replaced the right side cylinder head under extended warranty for $50 and completed repairs on 08/10/06.