Owners of other Ford or Lincoln vehicles such as the Explorer, F-150, Escape, EcoSport, Transit, F-350, F-250, Edge, Flex, Ranger, Fiesta, Focus, Fusion, Mustang, Bronco, Super Duty, Navigator, Continental, MKZ, MKX, MKC, MKT, Aviator, Corsair and Nautilus may also find these DIY instructions to be helpful.

The genuine Ford OEM (original equipment manufacturer) spark plug part number listed in the owner's manual is specified as being Motorcraft SP550 (also known as part number SP-550, CYFS-12Y-PCT or CYFS12YPCT).

A few other compatible replacement aftermarket spark plugs with their part numbers are as follows: ACDelco 17 Platinum and the Champion 9016 Iridium. The Motorcraft SP578 iridium may also be used (also known as Ford CYFS12YPT).

The tools and other items needed to complete this procedure include a deep well 10mm socket with a 1/4" or 3/8" drive ratchet or a 10mm wrench, an 8mm socket with a 1/4" drive ratchet, a 5/8" spark plug socket with an extension bar and a 3/8" drive ratchet and a tube of dielectric grease.

The first two steps are to open the hood and then locate the foam rubber engine cover.

Set the two nuts aside in a safe place.

Pull out the mounting bar at the rear of the engine cover from the two "C" shaped sockets.

Set the engine cover aside in a safe place.

Once the cover has been removed, you'll have easy access to the three ignition coils on the driver side and the other three coils on the passenger side of the motor.

If you have access to compressed air or a wet/dry shop vacuum, thoroughly clean off the top of the engine to help reduce the risk of having debris or other foreign items fall down on to the spark plug well or into the cylinder.

To further reduce the risk of having debris fall down into the engine, I recommend only checking or changing one spark plug at a time.

Gently slide back the white plastic locking tab on the electrical connector to unlock it.

Push down the release tab before sliding the electrical connector straight off the base of the ignition coil assembly.

I found that using a short extension bar on the ratchet kept my knuckles from getting scraped.

Set the ignition coil bolt aside in a safe place.

Gently rotate the top of the ignition coil assembly back and forth a few times to make sure the rubber dust boot isn't stuck or "frozen" to the top of the old spark plug if it hasn't been detached in 100,000 miles.

The OEM ignition coil part number is HL3E-12A366-AB (also known as B1812402721 or HU7E-12A402-AA DSVYA 21).

Inspect the rubber dust boot and the plastic housing for any damage, sludge or oil residue.

Set the ignition coil aside in a safe place.

If your gauge cluster has a SES or CEL (service engine soon or check engine light) warning message displayed, use an OBD II Scanner (also known as an OBD 2 scan tool) to check for any ignition coil related DTC (diagnostic trouble codes) such as P0350, P0351, P0352, P0353, P0354, P0355 or P0356.

Attach the 5/8" spark plug socket to a six inch or longer extension bar and the 3/8" drive ratchet.

Lower the socket into the well and push it over the top of the old spark plug.

Carefully loosen the old spark plug by turning it in the counterclockwise direction.

If you have trouble loosening a stubborn or stuck old spark plug due to corrosion (rust) or debris, try warming up the engine for a few minutes and / or spraying a very small amount of penetrating oil down into the spark plug well.

Allow the penetrating oil to seep into the threads for at least a few minutes before attempting to loosen the old spark plug again.

Once the spark plug is loose, detach the ratchet from the extension bar.

Carefully lift the old spark plug out of the well and detach it from the socket.

Inspect the electrode end of the old spark plug for any sludge, oil, soot, or overheating damage.

If the old spark plug is covered in soot or sludge, the engine might be burning oil and should be inspected by a professional.

If the old spark plug is white and ashy looking, the engine may have been subjected to overheating and the cooling system should be checked.

I recommend buying the original genuine OEM Ford iridium tipped spark plugs which are part number Motorcraft SP550.

If you have a spark plug gap gauge tool, check the gap on the new spark plugs. The SP-550 plugs should be gapped to 0.031".

The specifications for the SP-550 plug list an acceptable gap range of  0.027" to 0.031" (0.70-0.80 mm).

Be sure to check the specification on the product box if you are using aftermarket plugs.

Most spark plug manufacturers do NOT recommend using anti-seize lubricant on the new spark plugs since it can easily lead to over tightening which can result in damaging the spark plugs or the threads in the cylinder head.

Push the new spark plug into the socket.

Your socket should have a rubber insert or a strong magnet to securely hold the plug in place.

Carefully lower the new spark plug into the cylinder head. Try to avoid banging the electrode tip against the side walls or the top of the cylinder head.

Spin in the new spark plug by hand to help prevent it from becoming cross threaded.

Once the spark plug bottoms out against the spark plug, attach the extension bar and a 3/8" drive ratchet.

If you are re-installing the old spark plugs, just tighten the plug to a small fraction of a turn past finger tight.

If you are installing new spark plugs, carefully tighten the spark plug until you feel the new crush wash collapse which should be just a small fraction of a turn past finger tight.

If you have a torque wrench, the service manual's torque specification for the spark plugs is 133 in-lb (inch-pound) or 11 lb-ft (pound-feet) or 15 Nm (Newton meters).

Double check that the spark plug is tight before moving on to the next steps.

The dielectric grease will help keep out any moisture, dust or debris and ensure a reliable electrical connection.

Lower the ignition coil down into the well and push the rubber dust boot over the top of the new spark plug.

Spin in the ignition coil bolt a few turns by hand in the clockwise direction to help prevent it from becoming cross threaded.

Avoid over tightening the bolt to prevent from cracking the plastic ignition coil housing.

Push the electrical connector on to the ignition coil.

You should feel or hear the power plug "click" securely into place.

Slide the white locking tab in towards the ignition coil to secure the connector in place.

Push the mounting bar into the sockets and gently lower the front of the cover down on to the engine.

Spin on the two nuts a few turns by hand in the clockwise direction to make sure they don't fall down into the engine bay and become lost.

Start the engine and listen closely for any strange sounds that might indicate an issue such as a disconnected electrical connector or a loose spark plug.

If you do hear an odd noise, immediately turn off the engine and double check your work.

Be sure to write down the spark plug change in your vehicle's service records.

The owner's manual specifies that the spark plugs should be replaced every 100,000 miles.

Please check out all of my 2018-2020 Ford Expedition DIY Repair & Maintenance Guides.