Yep, the Slowbaru is still hanging in there, only recently I’ve noticed that it’s felt a little sluggish at times. Add that to the occasional (it hangs around for less than a sip of coffee) flash of the check engine light and a sudden increased thirst for the petrol stuff and it looks like it’s time to swap out the spark plugs.
Luckily it’s a fairly non eventful job, once you remove everything else in the way first..

2005 Subaru Impreza spark plug change

You will need:

-A new set of spark plugs first and foremost. After reading through various options (and everyone has their thoughts) I figured the best thing to do here is see what I was already working with and go from there. In which case it’s a NGK BKR6E-11 x 4. I’m a big fan of NGK plugs and have used them in everything from the RX7 to the Stagea and was happy to see them here. $7 each AUD from practically any auto shop and away you go with the added bonus of the -11 meaning they’re already gapped and that’s one less thing you need to worry about.

-A socket set and a couple of extension options. If you’re doing this for the first time, you’ll find they’re in the EJ25 pretty deep!

-A 16mm deep socket for the plugs themselves

-A 10mm and 12mm socket for various things you need to undo along the way

-Some kind of magnetic grab tool to make fishing things out a little easier

-Gloves of some description

YOU WILL ALSO NEED TO DO THIS WHEN THE ENGINE IS COLD. LESS BURNS, HAPPIER MECHANIC. LET IT COOL DOWN ALREADY, SERIOUSLY.

Making some room to swing a ratchet first (aka how good is room to work?)

BATTERY SIDE

We’re going to remove the washer bottle here so undo the two 10mm bolts holding it in place and then lift it out of the way. There’s enough length in everything connected to it to not have to disconnect it completely. Once moved you have plenty of room to work here.

AIR INTAKE SIDE

If you’ve still got your factory air setup here, undo the bolts on the front scoop (10mm) then using a couple of extensions, undo the bolts holding it down deeper in the bay (12mm). Loosen these bolts and then with the socket still in place, use the magnet tool to help bring them out into the light. Now you can move the intake around to give you more room to work here.

Once these are out of the way it’s a good opportunity to vacuum out all the plant and tree matter that may have found its way into the engine bay. When I finally buy a house, the last thing I’m going to do here is chainsaw that tree down on the way out for filling all of my cars parked under it with not only stuff like this but the occasional bug and spider.

Now we’ve got the space, it’s Impreza spark plug change time!

-Pull the spark plug wire out of the hole and move it out the way

-Using a 16mm socket and long extension, undo the old spark plug. Now to get it out you can use the magnet tool although I had some luck putting the socket on the loose plug and lifting the ratchet up slightly, effectively dragging the plug up and out slowly.

-New plug goes in but don’t over tighten it, the last thing you or any mechanic wants is a broken spark plug that deep in your engine.

-Plug wire goes back in.

-Replace everything you removed to clear space earlier

-Test car, all going well the only step left is to write down when and at what mileage you swapped them over as copper ones like the ones I used above are good for roughly 10,000 kms and you’ll get a sense when you’re due to do this again.

While it’s highly unlikely you’re going to confuse the plug wire order on this (there’s technically only two ways it can possibly go here) if you’re doing this for the first time, maybe replace one at a time, putting the wire back in before you get to the next one. Luckily if you do stuff this up, it’s not hard to swap them back over again. All and all this took less than hour with most time putting stuff back in more than anything.

Edit – the CEL keeps popping up randomly

While the car feels slightly more responsive, the Check Engine Light still pops up and so today after work I used the two black plugs under the steering wheel to see what gives and wouldn’t you know it? It’s coughed up the numbers…for the knock sensor again. Yes less than a year since I last changed it, it’s failing again. Looks like I’m going to have to pony up for a genuine one this time, or buy another aftermarket one for the next 11 months. Sigh… (Well at least I know what it is now..)