Asked in
Mercury Grand Marquis

How do you change the spark plugs on a 2005 Grand Marquis?


User Avatar
Wiki User
November 18, 2010 2:35AM

First thing is to go purchase a set of Motorcraft Spark Plugs for your Mercury, a feeler gauge, and anti-seeeze compound in a tube. You can buy another brand if you wish but Motorcraft is the OEM plug. Start with the one easiest to get to. Use compressed air to blow debris from around the spark plug. Grab the spark plug boot connected to the plug and twist it back and forth while at the same time pulling it off. Only grab the boot and do not pull on the plug wire itself or you will break the wire. Once it is off, use the correct size SAE socket to remove the plug turning it counterclockwise. If it sticks and will not come out with normal pressure turn it back in and then out again. Keep going in and out until you remove the plug. Take the new spark plug and check the gap which should be pre-gapped at the factory, but check it anyway and make sure it is gapped at .054. After checking the gap coat the plug threads with anti-sieze compound. Screw the plug in by hand if possible or with a plug socket if necessary. Tighten the plug down to 22 ft/lbs torque. If you do not have a torque wrench use a ratchet and socket and tighten it down holding the ratchet near the socket and not out on the end of the handle. Tighten it until it is snug and do not leave it loose or over tighten. Replace the plug wire by pushing the boot back on until you feel or hear it snap in place. Repeat the procedure on all other plugs. Only do them one at a time and only remove the plug wire from the plug you are replacing or you will get confused as to where they go.