Plain and simple, the 5.4L is a high tech engine. While the block on the 5.4L and 4.6L are pretty much the same, the structure and technology of the engine is entirely different. While the spark plugs on a 4.6L can be challenging, it is still relatively straight forward. Spark plugs are where spark plugs typically are, the spark wires run to a distributor like youíd expect in any vehicle, etc.

The 5.4L features, as well as other high tech features, the lack of spark plug wires. Rather then having spark plugs mounted on the sides of the engine, wires running to a distributor, the spark plugs in this engine are on top of your engine, and are connected directly to the ignition coil.

Everyone has a different way of changing out the spark plugs, and everyone says there way is the best. I will not try to compete with everyone, because each method has its own advantages. For example, some people donít take off the fuel lines, which takes that off the installation but it makes removing the coils more difficult if not nearly impossible. Using my method I try to make it as easy as possible and prevent breaking anything while in there.

There is also a lot of debate as to what spark plugs are best. There are some who swear by high-end spark plugs such as Bosch Platinum +4ís or Denso plugs, and some that swear by standard Ford Motorcraft plugs. I decided to use the same OEM plugs that came with the truck, Motorcraft platinum plugs. You can be assured when using OEM equipment that you shouldnít have any problems that you can blame on the plugs.

Tools you will need for this job are a 7mm, 10mm, 5/16", 5/8" deep and 5/8" spark plug sockets. The spark plug socket has a special rubber fitting inside, which grabs on to the spark plug, which is required to remove the recessed plugs from our engine. You will also need 1/4" and 3/8" universal joints and various 1/4" and 3/8" extensions. A spark plug gap tool can be purchased for under a dollar, and will prove valuable when setting the gap on the spark plugs. You will also need a tube of anti-sieze to apply to the threads of the new spark plugs. For different jobs you may need needle nosed pliers, a flat head screwdriver and other various tools.


Always be sure to remove your negative battery terminal prior to doing any work on the truck! Part of the procedures requires some gasoline spilling into the engine, as well as many points where a metal tool could come in contact with the body and an electrical source causing spark or worse, fire or personal injury. To avoid any such disasters, it is much easier and safer simply to remove the negative terminal prior to any work being done. Also, as a caution, do not over torque the spark plugs or the bolts attaching the coils to the head. Unfortunately I did so and ended up making the project much harder when I snapped a bolt off that held the coil to the head. Remember that you will always do much more damage by over tightening a bolt too much then you would by not tightening it enough..

  1. Using your 10mm and 5/16" sockets, remove your throttle body cover. This will give you better access to what you are working on. Also, I found it much easier to remove the bracket attaching the power steering pump for easier access to the plugs. This bracket is attached with three 5/16" bolts, and can be dangled out of the way, as it connects to one of the vacuum lines.

  2. Removing bolts for power steering fluid reservoir

  3. Using your 5/16" socket, remove the two bolts attaching the fuel line to the head of the engine. Once sockets are removed and set aside, pry the fuel line CAREFULLY away from the fuel injectors. Use caution to prevent damage to the injectors and the o-rings around the injectors. Beware that some gas will spill out when you remove the lines. Because of this, smoking or having an open flame (or even a hot trouble light, etc.) while working on the spark plugs is a definite do not do! If you ever want to upgrade to better injectors, now would be a good time to do so, you can simple pull them up to remove them from the engine.
  4. Pry the fuel line up and out of the way as far as you can without bending or breaking the line.
  5. The coilís are mounted with 7mm bolts, in between the injectors. If you arenít sure which is which, the injectors are orange and have blue o-rings, the coils are black and typically have yellow sticker son them (see below picture). Depending on the location of the coil, you may find it easier to use a univeral joint or a series of extensions to loosen and remove the 7mm bolt. After loosening and removing the bolt, you can unplug the electrical connector from the coil, and pull the coil out of the head.

  6. Removing the coil from the head. (A) Fuel injectors, (B) Coil

  7. After removing the coil, you can begin work on removing the spark plug. I find it to be a good trick to use to blow some compressed air in the hole or vacuum the hole out, to loosen any trapped dirt and prevent it from dropping into the engine.
  8. Because the spark plug sits so recessed in the head, it is a good idea to attach a 6" or 9" extension to your spark plug socket. You may need more extensions so make sure you have enough prior to starting the project. It is also important to note that the spark plug does not sit perfectly vertical, it is at an angle, facing the rear of the truck. If used properly after removing the spark plug, the spark plug socket should hold on to the spark plug, allowing for easy removal. (see below picture)

  9. Spark plug being held by spark plug socket, after removal

  10. Once you have removed the old spark plug, it is time to prep your new spark plug for installation. This involves gapping the spark plug and placing anti-sieze into the threads. To gap the spark plug, use a spark plug gap tool (can be bought for about a dollar at any auto parts store), and slide the spark plug along the tool until you reach the desired gap measurement. For the F-150ís, the recommended spark plug gap is between .052 and .056 inches. You can also use a feeler gauge for a more precise measurement. You should place some anti-sieze on the threads to not only make it easier to remove next time you do the plug, but also helps keep the seal better then without anti-sieze, and prevents rust from forming in the head.

  11. Setting the spark plug gap and placing anti-sieze on the threads

  12. Once your spark plug is prepped, it can be installed. Unlike some spark plug jobs, reinstalling the spark plug is just as difficult as uninstalling it. Reason is you canít just put the plug back in the spark plug socket and reinstall it. If you do so, the spark plug socket will grip on to the plug, and you wonít be able to get your socket out. The method I used was placing the spark plug in the spark plug socket slightly, but not into the bolt portion of the plug. By just placing the plug in deep enough so the socket wonít drop the plug, you can get the threading started, but remove the tool after a few turns with the socket. After starting the threading with the spark plug socket, switch to the standard 5/8" deep socket and torque down. Because the standard socket wonít grip on to the spark plug, you will be able to pull it away from the spark plug after tightening it down.
  13. After the plug is installed and tightened down, reinstall the coil, reconnect the electrical connector for the plug, and reinstall the 7mm bolt. Repeat procedure for the following plugs.
  14. Some plugs you will find are easier to replace then others. As mentioned previously, I had to use several extensions with a universal joint to safely remove the rear spark plug.

  15. A variety of extensions and universal joints may be needed to access the rear most spark plug.

  16. Once all spark plugs on one side have been replaced and all coils are bolted down, you will need to reinstall the fuel line. To do so, carefully place the fuel line into position over the fuel injectors and snap over the injector o-ring. Secure with 5/16" bolts that were removed previously, and visually inspect for tightness.
  17. Repeat the same process for the spark plugs on the other side. Once completed, give yourself a good pat on the back, knowing that you just saved yourself about $250 in labor!
Spark plug document written by Matt Adams. Please do not copy, distribute, post, or steal without my permission.