Subaru WRX Forum banner

How to change your sparkplugs

366K views 261 replies 97 participants last post by  Teawrecks 
#1 ·
Figured this might be helpful for somebody. First you'll need to properly gap your selected spark plugs- factory calls for .028-.031 gap, yours may vary depnding on model ie iridium or needs. Lots of info out there on choices of plugs- I won't go into any of it here.

You'll need to use some kind of gapping device and you'll want an accurate gap. Here's the tool I use:
 
#77 ·
As this thread is concerning spark plugs you want a flex head spark plug socket for sure- also the locking extensions I pointed out are helpful as well.

In general I use my flex head sockets a lot- I have set from 10mm, 12mm, 14mm, 17mm (3/8" drive).

I've got a couple of flex head ratchets as well.
 
#78 ·
Big Sky WRX said:
As this thread is concerning spark plugs you want a flex head spark plug socket for sure- also the locking extensions I pointed out are helpful as well.

In general I use my flex head sockets a lot- I have set from 10mm, 12mm, 14mm, 17mm (3/8" drive).

I've got a couple of flex head ratchets as well.
Flex head sockets are great. I need to pick up a nice set for working on the sube.

I've also found this to be invaluable. Wobble Extension

Just right if you just need a little bit but if it's in a tight spot where you can't get a hand to hold a universal joint.
 
#80 ·
today i'm installing NGK iridiums and next month i'm installing a VF39 with supporting mods and protune for the AP.....would these plugs be good for my application...and also the person at the auto parts store where i purchased my plugs told me they come pregapped at 0.44....i think i'm going to close that a bit to 0.34 or .035....any input on this?
 
#81 ·
I'd suggest w/ the turbo upgrade (and the subsequent increase in hp) to go one step colder.

Also you have the wrong plugs if they are .044, you want them ~ .028. Find plugs that come pre-gapped closer to .030. When you close the gap too much the angle is ususally less than optimum- w/ iridiums you also run the risk of damaging them.
 
#82 ·
Good info and nice work on putting it together. Well I have 65K on my stockers and haven't had any problems yet! Of course I am stock except a TB exhaust. Car runs fine and doesn't run rough. I drive spirted at at times but not abusive.

Been meaning to get to replacing them but been busy. Hopefully there not that different from my old 00RS. I am always good about maintenance but let my plugs go longer if all is well. Thanks for the insight.
 
#83 ·
Ive already changed my plugs once at 30k and I bought them from the dealer and checked em out and the gap was right. I just ordered a set of 1 step colder and Im concerned about gapping. I have a gapping tool but if I need to adjust the gap how do I do it? Just usr pressure to close the gap? I dont want to break anything.
 
#84 ·
If the gap is very large- I consider taking them back for a closer fit. There are some plugs that are gapped too large IMO. It's almost impossible to get a good even gap w/ those.

If it's just a litlle wide, tap the plug gently on a firm surface- measure, tap again if necessary.
 
#85 ·
Big Sky WRX said:
If the gap is very large- I consider taking them back for a closer fit. There are some plugs that are gapped too large IMO. It's almost impossible to get a good even gap w/ those.

If it's just a litlle wide, tap the plug gently on a firm surface- measure, tap again if necessary.
i had to do this with dealer plugs. they were close to .040 i believe.
 
#87 ·
...Just got done changing my plugs, thanks, I wouldn't have been able to figure it out on my own (I probably could have, but I don't like to just go taking things apart!).

I found that a 1/4" drive works way better than a 3/8" flex socket to take the coils off. The 1/4" drive I have (ace hardware) fits right down in there.

If you have a variety of tools to work with, it makes the job easier (obviously), I was swiching back and forth between different ratchets, because this one won't fit in the space, or that one isn't long enough, etc.

Just my $0.02!

Big thanks again!
 
#88 ·
Finally did the plugs last weekend for the first time on the car using this post as a guide. A bit overdue at 108K on the OEM plugs. Went very smoothly, so thanks!

However, did not need flex sockets. Got it done with a 3/8 drive and a short locking extension. Only trick was to get the drive off the socket a few turns after loosening (flat blade screwdriver helps) and do the rest by turning the extension by hand. Even found enough room to get a mini torque wrench on the plug and the coil pack bolt for tightening up again. :cool:
 
#89 ·
I'm about to get a set of plugs to attempt this. I was looking up plugs on sparkplugs.com and they have NGK platinum and double platinum. It says that the double platinum are the OEM plugs and are 11.71 as opposed to 2.68 for the regular platinum. Which ones should I go with?
 
#91 ·
Well at my pepboys the stockers list for 28.11 each (which means the sell price is around 14 each). I bought a set of the iridiums (not the -11 ones) at 7.00 ea. I used the same gap tool in the picture above to check them, they are at .25. I gapped them to .30 carefully, not putting pressure on the tip but using the lip of the grounding electrode to pull up slightly with the gapper's edge (actually the tool is called "the gapper"). You have frightened me that I may be damaging the tip even if I touched it gently with the gapper. I dont see any damage and I was very careful. I'm really thinking of getting a feeler gauge to check the gap because of the incline. If I dont see any damage, you dont think I did anything to them do you? I looked and looked on many sites, but I couldnt find any definitive information on the process of gapping these types of plugs other than the "be careful" warning. If I keep the gap to .29-.30 I should have any issues right? I had to touch the center electrode with the gapper to make sure I was in spec, but I was gentle and slow about it. Whats the consensus on that? I could see if you used a prong to gap and wedged it against the iridium tip how it would break, but I didnt do anything of that nature. Hell, they're goin to get hit by some pretty hot explosions in the chamber anyway if anything should break something that fragile, that should... I dont want to have to go yanking plugs back out since they're not the easiest to get to.
BTW, mostly stock I am yes....
j
 
#92 ·
http://densoiridium.com/installationguide.php

oh well, i already gapped the damn things from .25 to .30. I cant see any damage after close inspection. i guess i'll install them tomorrow and find out. The ONE thing that would scare me about a plug like this is if the tip were to break off into the combustion chamber. That tiny tip could score the wall or cause other damage. i used similar ones in my sentra and i got oem performance, and thats all I want from something like this.
 
#93 ·
For those trolling looking for some good specific plug info on the following.

NGK Iridium BKR6EIX (Stock 6418 at Pep Boys) 6.99 ea for EJ20

I just installed these. They come stock with a 0.25" gap. After reading that they might be outside the gap for a WRX, I gapped them. People warn not to gap iridium but if you are super careful, you wont have a problem. I gapped mine to a 0.29/0.30.00000000000

Do NOT put a gapping tool between the center and ground.
Do NOT force a gap checker inside the center and ground space. If it doesnt slide in easy, DONT FORCE.

Gap by pulling up on the lip of the grounding electrode with a gapper OR use a pair of fine pliers to lightly tug the sides of the center ground. You dont need too much force. Tap the ground electrode on a piece of wood to close the gap. The best way to check the clearence is measure with a wire gap checker. Use the .28 and keep it off the iridium tip. Do this over a white surface so that you can see the hairs width of space from the .28 wire and the head of the center electrode to ensure its a .29. Make sure the gap is close enough that a .30 will NOT fit in and that a .28 will fit in and leave a seriously small hair's width of space between the measurement wire and the tip of the iridium. You may notice that after the iridium tip is exposed to breath, or air, that it tarnishes quickly. Dont let that alarm you, it freaked me out but it seems that iridium tarnishes from the silver color on the boxe's picture to a dark color easily.


My car is running fine. No misfire, no sputter, like stock. My driver's side stockers with 62k on them were NEEDING the replacement.
 
#94 ·
I was just curious if the flex spark plug tool you used was a 5/8 socket. I am pretty sure that is the size the NGK plug takes but there are so many sizes out there that I just wanted to make sure.
 
#99 ·
Just did mine over the weekend. Not a bad job at all.

I put the NGK iridiums in it. I checked the gap with a feller gauge and they were fine so I left them. Car is running great. I had 70k on the originals.

I still dont understand why the iridiums are cheaper than the oem double plats but oh well I dont really care I guess.

Oh and good guide I read it before I started and had no issues :thumbup:
 
Top