.050 inch according to motorcraft.com but my Chilton repair manual shows .044 inch
.050
8 spark plugs
8 spark plugs
According to one of Fords websites : For a 1993 Mercury Grand Marquis , 4.6 liter V8 engine : ( the spark plugs are gapped at .054 inch )
remove engine cover
.054 inch ( according to fordparts.com )
Remove the spark plug wires from your 2002 Mercury Grand Marquis spark plugs. Remove the spark plugs by turning them to the left with a deep well 5/8 socket. Reverse the process to install the new spark plugs.
The 1991 Mercury Marquis spark plug gap is .034. Most spark plugs will be pre-gapped by the spark plug manufacturer.
( 8 spark plugs ) for your V8 engine
Your local autozone can tell you. If they can't ask for spark plus for a 1988 Ford Thunderbird with a 5.0 engine.
maybe someone has a picture but the general rule if you want to find them is follow the leads that will take you upto the side of your engine where the spark plugs are
Start with the ign. wires and the spark plugs.