HOW-TO: Replace Spark Plugs and Engine Air Filter (45k maintenance)

Grab the upper air box and pull it up and away from the lower air box. Then pull the upper airbox to the right, separating it from the air intake tube.





Next, we must prepare to remove the air intake tube. There are several connectors that must be removed before we can move the air intake tube.



Use a pair of pliers to squeeze the spring-style hose clamp on the top right of the air intake tube. You can easily pull the hose off of the barb when the hose claim is squeezed.







To the left of the hose barb exposed by removing the previous tube, there is another hose with a 90-degree connector. Disconnect this by squeezing both sides of the ring where the ridges are. The connector will slide up and off when squeezed. Use care to remove the hose without breaking the clip.





To the left of the hose you just removed is an electrical connector. Squeeze the connector and pull to the left to disconnect it.

Continuing left, there is another electrical connector that must be removed. A small flat blade screwdriver can help pry the locking tab up. Once sequezed, the connector should release.





Above the electrical connector we just disconnected, there is a medium diameter hose. This can be removed by grabbing the hose and pulling it away from the tube it is connected to.





To the left there is an electrical harness that zip-tied to a metal clip, which is attached to the air intake pipe. Use a small flat blade screwdriver to pry up on the metal clip and detach it from the air intake pipe.





To the left there is another, smaller-diameter hose. This hose has a permanent hose clamp. If you grab the hose and firmly pull outward, it will release.





There are two vacuum hoses routed above the air intake tube. Remove them from the clips mounted into the air intake tube.

At the bottom of the air intake tube, next to the turbocharger, there is another vacuum hose. Remove it from the clip.





Grab the air intake tube near the turbocharger and gently pull it to the left. It should release off of the turbocharger inlet.





Pull the air intake tube to the left and then rotate it up and towards the back of the engine bay so the small curved piece points upward. Then rotate on the transvere axis so the long pipe points up towards the hood, and then to the passenger side of the vehicle. While making this maneuver you can free the pipe from underneath the vaccum hoses and electrical harness that ran above the air intake tube.









We now have access to the ignition coils.

Use a Torx T-30 socket and appropriate ratchet or t-handle to remove the ignition coil bolts. I strongly suggest working one ignition coil at a time, rather than trying to remove all of them at the same time.





The ignition coil should pull up and towards the front of the engine bay.



Once removed, the ignition coil can be placed on the top of the engine, and you should be able to see the spark plug.



Use a 14mm spark plug socket and appropriate ratchet with extension or t-handle to remove the spark plug.





Despite only having 45k miles on them, they don't look great. I think Mercedes/Infiniti knew what they were doing when they picked the maintenance interval for this procedure. Here's the OEM spark plug next to the replacement.



Use the 14mm spark plug socket and appropriate ratchet with extension or t-handle to screw the replacement spark plug into its bore. Be careful not to impact the tip of the spark plug. Be careful not to chip the ceramic insulator of the spark plug. Be careful to seat the spark plug properly and ensure the threads engage smmothly. You do not want to cross-thread a spark plug!



Once the spark plug has been seated and hand tightened, use a torque wrench set to 17 ft-lbs (204 in-lbs) to tighen the spark plug.



Reattach the ignition coil and use a torque wrench to tighten the ignition coil bolts to 80 in-lbs.



Repeat this process for the remaining three cylinders.

Before putting everything back together, use this opportunity to replace the engine air filter. I like to vacuum out the lower air box, as well.







Installation of the remaining parts is the opposite of removal. When screwing the upper air intake lid to the lower air intake box, make sure you have aligned the two halves correctly. It's easy to strip the lower air box, so screw the airbox together carefully. It only needs to be tight enough to make a good seal. Don't yank on it like a gorilla.



When you're done, it should look exactly like it did before you started.