Impreza FB20 spark plug change advice

[Joe1]

My Impreza is getting close to 60k miles and l would like to change the plugs as a DIY project. I have watched some YouTube videos and it appears "doable" for my novice skill level.

I've changed spark plugs myself in a Mazda Protege, but that was easy as the plugs were easily accessible. The boxer engine is a bit intimidating to me for this job as l need to remove the battery and air box to get to the plugs. I had the dealership change them out on my previous Subaru Forester, but l am determined to not pay the outrageous prices this time.

I ordered the NGK OEM plugs from Rock Auto. I have a 14mm spark plug socket. The biggest concern l have is that the plugs are difficult to reach and the visibility during the installation and removal is not ideal. I have a bit of anxiety about taking this task on. I've been changing the oil and air and CAF filters on this car, but spark plugs will be a HUGE feather in my cap if l can pull this task off.

Any advice or words of encouragement will be greatly appreciated as l prepare to embark on this daunting task.

 

[dogememe]

What types of plugs come standard in Subarus? In my Escape I changed the plugs at about 65K miles and at first I thought it picked up like 0.5MPG but after a few tanks of data it ended up making no difference. My point is, I'd wait til 100K to change plugs if it came with Double Platinum or Iridium plugs. Otherwise you're just wasting money and time.

 

[RF Overlord]

If that motor has aluminium heads, get a decent torque wrench. If the OEM plugs are nickel-plated (shiny) then no anti-seize is required unless specified by Subaru, otherwise use a very sparing amount on the threads.

Start the plugs by hand for a few turns before tightening to prevent cross-threading.

Make sure the engine is cold.

Did I mention using a torque wrench?

 

[maxdustington]

Just take it slow, follow the DIY and take a break if you get frustrated. It's just spark plugs dude, all you have to worry about is cross threading them and that is easy to avoid if you stay focused.

First job I ever did on my own car was a 2.0 VW timing belt. I followed the DIY, took my time and it came out great. You can teach yourself how maintain/fix your cars.

 

[Omahaug]

There are a ton of YouTube videos on doing the plugs for boxer engines, I'd study those first.

They have a lot of tips on how to maneuver the engine to get access to the plugs, since sometimes the frame of the body blocks access for a ratchet to get anywhere near the plug hole.

1. Once you get it out, getting it in and not crossthreaded would be required (you need a spark plug socket so the plug doesn't fall off of it while you angle the plug into the boxer engine sideways).
2. Get a nice long ratchet so you can get the old plug out easier if you have the room to use it and not a stubby ratchet.
3. Use a torque wrench when putting it back in. Having it back out or having it overtightened is an avoidable disaster with a ten dollar torque wrench from Harbor Freight that works reasonably well.
4. If it's click type torque wrench, make sure you use a torque wrench of the proper drive for the torque spec, otherwise you won't feel the click and you'll go past it and bad things will happen. Most plugs are what, 14ft lbs or so (check your manual and make sure)? So you'd use either a 1/4in or 3/8in drive.
5. Test the torque wrench to make sure you can feel the click on the rated setting before attempting it on a plug. For example if you're doing 14ft lbs for the plugs, find another large fastener on this car (like a lugnut on a wheel) and try 14ft lbs of tightening. Lug nuts are usually 80 ft lbs or more so you should feel the click immediately and not tighten any further, get a feel for it so you know what to expect when actually doing the plug. In order for you to actually test a 1/4in or 3/8in click type torque wrench on a lugnut though, you'd probably have to use a socket that's going to require a 1/2in drive so you'll need a converter socket but you should already have those (if not, Harbor Freight). If you're testing 14ft lbs on an 80+ lugnut and you don't feel the click immediately, something is wrong with the torque wrench. Keep turning and you'll twist the drive right off the ratchet too.

 

[vssjim]

All Subaru's are very tight clearance to body the on the twin cam engines and are fastest done from the bottom removing front coil then rear coil then plugs, the single cam engines are quit easy over all just done from the top in a few minutes.
.

 

[joekingcorvette]

I have found when removing plugs to break them loose about a 1/4 turn then tighten a 1/4 turn and do this a couple times and keep going back and forth until they come out easily. I learned this from doing my old 5.4 Ford F-150 engine.

 

[Clarkbug]

I would also suggest getting a lot of different types of extensions and maybe a wobble or a universal joint. I had to put the socket and a small extension into the tube, and then connect to the ratchet, or then put on another extension.

This was on the 2.5, but I wouldn't think the 2.0 would be that different.