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5.8L F-150 Spark Plug Replacement

How To Replace Spark Plugs on a 5.0L/5.8L V-8





If you've replaced spark plugs before, changing them on a Ford Windsor V-8 (whether it's a 5.0L or 5.8L) is fairly straight forward and the engine bays on these vehicles have plenty of room to reach all 8 plugs without having to get creative. If this is your first time performing to procedure, take your time and follow the instructions below. Often times, the most difficult aspect of changing spark plugs is finding the correct tools to access confined spaces.


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• Disconnect the negative battery cable.
• The proper gap for the 5.8L Windsor in 1994 was .042"-.046". You can verify that the required spark plug gap by finding the emissions label under the hood. On our subject vehicle, the emissions label was located on the inside of the hood, driver side.

• The spark plug for a cylinder is located near the exhaust port for that cylinder. If you have difficulty finding one, simply trace the spark plug wires.

• Change spark plugs and plug wires one at a time. Do not remove all the spark plug wires at once. By replacing them one at a time, you do not have to worry about crossed plug wires, which can result in an expensive repair bill.

• Remove the spark plug wire from the spark plug. If the spark plug boot is deteriorating, do not worry, this is why we change spark plugs and plug wires at the same time (years of extreme heat will take its toll on the silicon boots). Sometimes the boots need a good wiggle to get them off, or you can use a spark plug boot removal tool to make it easy on yourself.
• With the boot removed, use a 5/8" spark plug socket to remove the spark plug. You may or may not need an extension to reach the spark plug. Check below for a list of extensions we used and for what cylinder.

• Be aware that the spark plugs are mounted at an angle into the engine block - you'll need to match this angle when installing the new ones, as you won't want to damage any of the threads.

• After removing the old spark plug, check the gap of your replacement plug and coat the threads of your new spark plug with anti seize.

• Install your new spark plug. Always hand start to thread the spark plug to ensure cross threading does not occur. Spark plugs get "snugged" up, do not overtighten.
• Apply a small amount of dielectric grease to the terminals of your new spark plug wire. Remove the old spark plug wire completely, then install the new wire, ensuring that the terminals are installed securely at both the tip of the spark plug and the distributor.


Cylinder #


Extension(s) Used


Passenger side, front (closest to radiator).

3" extension.


After number 1, moving from front to rear.

5" extension.


Between cylinders 2 and 4.

6" extension.


Passenger side, rearmost (closest to firewall)..

6" extension.


Driver side, front (closest to radiator).

3" extension.


After number 5, moving from front rear.

3" extension.


Between cylinders 6 and 8.

3" extension.


Driver side, rearmost (closest to firewall)

No extension required.