Replacing the spark plugs on a 2007-2010 Lincoln MKX with a 3.5L requires removing the upper intake manifold. Before I start a job, I like to use compressed air to blow off dust, debris, etc. to lessen the likelihood of anything entering the engine later on in the repair. This is not an overly complicated job if you take your time. The tools required to perform the job are pretty basic as shown in the picture below.
Begin by removing the beauty cover and air cleaner inlet pipe. To remove the air cleaner inlet pipe, there are two clamps with 8mm bolt heads that need to be loosened along with removing one vacuum hose that will simply slide out of the pipe and a PCV tube.
This is also a good time to clean the throttle body with throttle body cleaner and a toothbrush – this one was past due. I went ahead and removed the throttle body from the upper intake since it is only 4 bolts and 1 connector. This allowed me to thoroughly clean the inside of the throttle body and replace the gasket between the upper intake and throttle body.
Next, disconnect the evaporative emission tube, brake booster vacuum hose, and the PCV tube from the intake manifold (the PCV tube slides off the port coming out of the rear valve cover). Detach the wiring harness retainers from the upper intake manifold, and disconnect the electrical connector that is on the backside of the intake manifold (squeeze and pull to release the connector). Next, remove the two 8mm bolts that support the upper intake manifold – one is attached to the area where the throttle body attaches and one is attached at the center top of the intake manifold; both are shown in the pictures.
Remove the remaining six 8mm bolts that hold down the upper intake manifold and it will come out with relative ease. Make sure to clean the lower intake manifold mating surface and cover it. Next, clean the openings of the upper intake manifold and replace the gaskets – old ones were green but new ones were blue.
Also, as rule of thumb, cover the two open ports coming from the valve covers to insure nothing enters the engine through them.
Once the manifold is removed, disconnect all 6 electrical connectors from the ignition coils and then remove the 6 8mm bolts that hold down the ignition coils. May take a little bit of wiggling to slide the ignition coils out of the holes but they’ll come out. Once removed, look over the ignition coil boots to make sure there are no cracks or worn spots that could cause arcing which would lead to misfires. After this, use a 5/8″ spark plug socket, extension, and ratchet to remove all 6 spark plugs.
Install the new spark plugs (I prefer to go back with the factory Motorcraft spark plugs) tightening them to 133 in. lbs. Then, install the ignition coils making sure to place dielectric grease over the ends that mate up to the spark plugs. I also add a bit of dielectric grease around the ignition coil seal as it makes it easier to slide down into the valve cover hole. Tighten the ignition coil hold down bolts to 62 in. lbs. and re-attach the electrical connectors using a dab of dielectric grease over the face of each. Now your ready to re-install the upper intake manifold remembering to tighten the 6 hold down bolts from the center of the intake manifold working your way out – torque them to 89 in. lbs.
Once the upper intake manifold is re-attached continue connecting and re-installing what you have already removed in the reverse order. In the end you should have the below used parts left over: 3 upper intake manifold gaskets, 1 throttle body gasket, and 6 spark plugs.