The Ultimate Subaru Spark Plug Replacement Tutorial

Whether you’re replacing your spark plugs as routine maintenance, or you’re replacing a bad spark plug, you came to the right place.

Replacing spark plugs is something you can do at home within an hour as long as you have the following tools:

  • Appropriately sized spark plug socket
  • 8-10mm sockets
  • Ratchet and extensions
  • 10mm wrench
  • Floor jack and a piece of wood (optional)

The steps you need to take are as follows. Keep in mind that this set of steps is based on the Subaru Legacy, but you should be able to follow it pretty easily with another Subaru model.

1. Order OEM Replacement Spark Plugs

Before you can start anything, you need replacement spark plugs. Even though you may only have one bad plug, we recommend replacing all of them at once. If one plug has gone bad, the others aren't far behind. Also, it's more cost and labor efficient. When ordering plugs, It’s important to find the right part number for your exact Subaru model. If you accidentally order a spark plug made for another Subaru model, it won’t work quite as well as it should.

The good news is that it’s pretty easy to find the right OEM spark plug for your Subaru. Just check out our catalog of genuine OEM Subaru spark plugs and then do a search on your model. When you get your replacement spark plugs, you can proceed with the rest of the steps.

2. Remove the Air Filter Housing

Open the hood. Pop off the mass airflow sensor by pinching it and then pulling it off. Next, remove the 8mm screws holding the hose in place and disconnect the wires. Pop the hose out and then remove the air filter housing.

3. Lift the Engine (Optional)

To make it easier to access the engine, you can lift it up by about an inch. This step isn’t mandatory, though. If you don’t mind bending over a little extra, you can skip this step. If you want to go easy on your back, here’s how to lift the engine:

  1. With a long extension and 14mm socket, remove all the 14mm bolts holding the motor mounts in place.
  2. Slide the floor jack underneath the engine. Insert the small piece of wood between the floor jack and the oil pan, and then lift the engine by about an inch.

NOTE: Make sure the floor jack doesn’t crush the exhaust. Also, don’t lift past the top of the motor mount studs.

4. Remove the Ignition Coils

With a 10mm socket, unbolt each coil, then pull them off the spark plugs.

5. Remove the Spark Plugs

With a 14mm spark plug socket and short extension, remove the spark plugs.

6. Install the New Spark Plugs

Image Credit: CarsNToys

Simply screw in the new spark plug with your hand until it stops. Next, use a wrench to turn it halfway. Don’t over-tighten it. Of course, repeat the process for the other plugs. Next, wrap it up by reinstalling everything in the reverse order of removal. More specifically:

  1. Reconnect the ignition coil(s).
  2. Put the engine back down and then the motor mount nuts. (Do this only if you lifted the engine in the first place.)
  3. Put the air filter housing back in place.

If you have any questions about replacing your spark plugs, you’re welcome to reach out to us. We’ll be glad to assist you.