The 1991 Mercury Marquis spark plug gap is .034. Most spark plugs will be pre-gapped by the spark plug manufacturer.
.054 is the gap for the Mercury Grand Marquis.
On a 1997 Mercury Grand Marquis : Check the Vehicle Emission Control Information ( VECI ) decal in the front of the engine compartment , for the type of spark plug used and the spark plug gap
Remove the spark plug wire from your 2001 Mercury Grand Marquis. Remove the spark plug with a 5/8 deep well socket, white turning it to the left. Reverse the process to put in the new spark plug.
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 )
Each spark plug has a coil on the top. Just remove the coil.
The correct spark plug for the 1991 model, 200 hp Mercury outboard, is a NGK brand, BU8H.
need to know the spark plug gap for a 1979 Mercury Grand Marquis with 351 modified.
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.
According to one of Ford's websites : For a 1991 Mercury Cougar , 3.8 liter V6 : ( the spark plug gap is .054 inch )
firewall 4 - 8 3 - 7 2 - 6 1 - 5 front of 2002 Mercury Grand Marquis
pre-heat spark plug, if this works then replace it.
According to one of Fords websites : For the 1.6 liter / 98 cubic inch four cylinder engine in a 1991 Mercury Capri ( the spark plug gap is .044 inch )