Spark Plug Changing - Instructions

kastle · 01-14-2002, 10:10 AM

To remove the plugs, I used was a spark plug ratchet (the type that hinges at the head), a 3" extension and a 1 1/2" one. Of course I used a 5/8" spark plug socket too. I found it necessary for the tight spot plugs to put the socket down the spark plug hole next the 3" then the 1.5"; and put the ratchet on that. Kind of a pain but I couldn't think of any other way to do it. Getting the whole thing out when you're done is fun too. I used a magnet and some needle nose pliers to grab the parts. Depending on your tools it may be very hard to get the ratchet, socket and extensions apart when they are down in the motor. Sometimes you need to use a long flat bladed screwdriver to get between the tools and twist to separate them. The ones on the passenger side don't leave much room. On the drivers side Take out the washer fluid bottle first before doing any plugs. It makes it easier even for the front one. Disconnect the wire from the pump and take off the 2 screws. It lifts right up but, undo the hose at the bottom and put your finger over the hole first. You can lay the tank with the hole up and it shouldn't leak out. While I've done the plugs on that side with the battery in place I find it easier if you take the battery out too.

On the drivers side (LHD) it's necessary to remove the Air Filter box if you have an MAF system like an older style Impreza, WRX or Forester XT. Please look here:

http://www.scoobymods.com/forums/showthread.php?t=4142

To see how to remove the airbox. While that's for the H6 it's similar with the exception you need to unplug the MAF from the airbox.

Just a few things I do when doing plugs in general. Change plugs on a cold motor. Twist the wires boot right and left a few times to loosen them. You gotta tug really hard on those suckers to get them off. Grab the boot and not the wire when doing this.

I check the gap on the plugs to verify they are OK. I put dielectric (SP?) grease on the end of the plug (the end the wire goes on) as well as the ceramic. I also use some never seize on the threads. I've heard differing opinions on this but I haven't had problems doing it. That's my version anyone have a better way let me know.

One last thing, always tighten the plug in there by hand first to be sure you haven't crossed the threads. For the torque spec. on the plugs it's 15 ft/lbs but to be honest I could never get a torque wrench in there so I do it by feel. Consider there is a crush washer so after contact you need to crush the washer then you will feel more resistance. I go just a little past that.

Peaty

Again for some WRX specific info look here:

http://www.scoobymods.com/forums/showthread.php?t=511

for some H6 Legacy info look here:

http://www.scoobymods.com/forums/showthread.php?t=4142

Peaty · 03-01-2002, 01:47 PM

Mike (ChosenWon on the i-club) was nice enough to let me steal his pics and directions on doing a spark plug swap. I think he did a nice job, thanks Mike:

-------

Even with most of the stories of quick and easy success that most of the members have had with changing plugs, I was still very nervous about changing my own. With some guts and encouragement form Peaty, I finally took the plunge and did it myself. I am glad that I did as well. It is as easy as they say. It did take well over an hour though. Of course I was taking pics, chasing down more batteries for more pics, going in for a coke, and chaning the plug wires as well. I will show some basic pics here.

Anyway, Here is what you will need: 1- 3" extension and a 1 1/2" one, 1- 5/8 spark plug socket (crucial) 1- Swival head socket wrench note: You can of course use a straight wrench but in order to get around a couple of the angles you will eithe need a swival socket extension.

Peaty · 03-01-2002, 01:48 PM

1- tube of anti-seize 1- tube of dialectric grease/silicon lube don't buy hte little packets. Waste of money. Buy the tubes. The total for what you see below was like $6. In retrospect I wish I had gotten the bigger tube of silicon grease. Oh well.

Peaty · 03-01-2002, 01:49 PM

Take out the windshield washer resovior. I have been planning this and ran myself out of fluid to make things easier for me. I took out the 2 top screws,

Peaty · 03-01-2002, 01:51 PM

and unhooked the pump's electrical connection. simply pinch the plug as will most automotive connections.

Peaty · 03-01-2002, 01:52 PM

Since I was out of fluid I did not force the issue with the small rubber house that was attached to the tank. It was being a pain and could see that it would be a pain to get it re-attached, so I simply left it attached and laid it out of the way.

Peaty · 03-01-2002, 01:53 PM

Once you get the resovior out the the way, it is fairly simple to get at the plug wires. Of course pull on the boot and not the wire. Pictured below is the forward most plug on the drivers side. The most challenging of all of them to get to. I found it necessary for the tight spot plugs to put the socket down there, the 3" then the1.5"; and put the ratchet on that; slid it into the hole. It was well designed, and has a tight tollerence. The socket slides onto the plug easily.gently push the socket onto the plug and twist untill you feel it "lock".

Peaty · 03-01-2002, 01:54 PM

Then attache your wrench and get it out of there. It came out pretty easily.

Peaty · 03-01-2002, 01:55 PM

I had a problem getting the loom holder to latch back as you can see here, because the mag wires are so much thicker than the regular wires.

Peaty · 03-01-2002, 01:57 PM

Just a quick example of the difference between the Mag wires and the oem wires.

Peaty · 03-01-2002, 01:58 PM

here is a comparison between the crapion plugs and the NGK plugs.

Peaty · 04-18-2002, 07:23 PM

Here are the type of plugs I like to use in my RS. They are standard copper type. From what I gather copper is the best performance wise. Copper conducts better than plats. They just don't last as long as Platinum plugs. I change my plugs every spring. They only cost 1.50 each and it's not that hard. Platinum for longevity (I put some plats in my Outback) and Copper for performance

Peaty · 05-18-2003, 05:46 PM

Something that comes in real handy is a magnet to remove plugs once they are loose.

Peaty · 06-22-2003, 12:58 PM

FYI - 02 WRX OEM Spark Plugs:

Subaru PN: 22401AA530 = NGK PFR6G

Peaty · 03-07-2004, 09:17 PM

WRX coil on plug setup unlike the motors with spark plug wires. The swap is the same for the most part though.

Peaty · 03-07-2004, 09:17 PM

coil out and off of plug

Peaty · 05-12-2004, 01:57 PM

Dear Peaty, When I change the plugs in my Forester I usually use about a 6" piece of 3/8" rubber gas line tubing to retrieve and thread the spark plugs into the manifold opening. Which as you know can be be a difficult task to the layman. This is an old mechanics trick I learned a long time ago and never forgot. I use it alot. Try it, it really helps preventing cross threading.

Unabomber · 04-28-2005, 09:03 PM

Just changed the plugs in my car today. The advice offered here and on the other couple of spark plug pages is great. I will add that having a mid-well 12mm socket would help a ton. For you tool n00bs, mid-well is a newer socket style between a short one and a deep-well. I was cursing my buddies tool set for not having a mid-well. The need for it is apparent as you don't get enough engine clearance with a short socket and a deep one or short + small extension will give you too much and put you into the engine well. I made due with what my buddy had, but it would have been FAR easier with a 12mm mid-well socket.

Peaty · 08-15-2005, 05:21 PM

Another helpful tip from 2k2blackwrx:

Hey Peaty, I finally Changed my plugs today and I wanted to add a few tips.

First off, on the WRX with the Coil on pack the White harnass will be on the coil that is closer to the bumper for the WRX. This has to be put on correctly for the firing order.

Also I had a 3 inch extension for the spark plug to remove it and I found it was too long! My ratchet would not fit in there with the 5/8 inch spark plug socket and the 3 inch extension because of the engine well. Luckily I happened to have What I believe was a 2 inch extension, this will work PERFECTLY because it just sticks out the end of the hole where the spark plug is and you wont have any trouble with the ratchet.

Also, remember to reattach the ground wire on the passenger side coil screw. I think it is somthing easily forgotton as I did and then you will have to remove your airbox to reattach it.

Blk_RS01 · 05-08-2006, 10:09 AM

I just changed out my plugs and wires today and..

for those who might not have tools.. advanced autoparts have this tool set for only 7 buck and it comes with the right sockets (with magnets inside them already/extensions and even a tilted wrench

Peaty · 12-31-2006, 09:19 AM

A few random shots from when changed the plugs in my Forester XT (2.5L turbo)

Peaty · 01-16-2007, 05:37 PM

As for brands NGK are what I like to use. I feel ND are good too. Spark Plugs typically come on three flavors. Copper, Platinum and Iridium. From what I understand (someone please PM and correct me if I'm not right here)

(FWIW it's not uncommon to find that your Subaru came from the factory with Champion plugs)

Copper:

Pro: Inexpensive ($1.50 ish), Very Good spark, good performance plug,
Con: Not very long lasting, you need to change them more often 15K miles or so. (I'd change them yearly myself)

Platinum:

Pro: Longevity, last longer than the coppers 30 or 60K miles depending on the application 3-5 bucks each best guess

Con: Spark is not as good as Copper, costs more than copper, 3-5 bucks each best guess

Iridium:

Pro: Performance of copper longevity of Platinum
Con: Cost is very high relatively speaking 11 - 15 bucks each best guess

Peaty · 02-14-2007, 06:36 PM

Some info on NGK Sparkplugs part number decoder.

Peaty · 07-17-2007, 06:21 PM

Some very good info from ScoobypHreak from over at my local KC Area subaru board: http://kcsubaru.com/

-------------------------

I hope this clears up everything on Plug info for WRX/STi owners

WRX owners:

Plug Maker/Type/Part Number/Car Type Used/Heat Range

NGK/Copper/BKR6ES/WRX/stock
NGK/Copper/BKR7ES/WRX/one step colder
NGK/Copper/BKR6E/WRX/stock
NGK/Copper/BKR7E/WRX/one step colder
NGK/Platinum/BKR6EGP/WRX/stock
NGK/Platinum/BKR7EGP/WRX/one step colder
NGK/Platinum/PFR6G/WRX/stock <----OEM plug
NGK/Platinum/PFR7G/WRX/one step colder
NGK/Iridium/BKR6EIX/WRX/stock
NGK/Iridium/BKR7EIX/WRX/one step colder
Denso/Iridium/IK20/WRX/stock
Denso/Iridium/IK22/WRX/one step colder
Champion/Copper/RC10YC4/WRX/stock
Champion/Copper/RC9YC4/WRX/one step colder
Autolite/Copper/3923/WRX/stock
Autolite/Copper/3922/WRX/one step colder
Autolite/Platinum/AP3923/WRX/stock
Autolite/Platinum/AP3922/WRX/one step colder
Autolite/Platinum/APP3923/WRX/stock
Autolite/Platinum/APP3922/WRX/one step colder

Some STI Plug Info
NGK IFLR6B (Iridium)--Subaru STI OEM Plug

NGK PLFR6-11 (Platinum)--used by a prominent tuner on his car

NGK LFR6AIX-11 (Iridium IX)
NGK LFR7AIX-11 (Iridium IX)--"one step colder"

Denso IKH20 (Iridium)
Denso IKH22 (Iridium)--"one step colder"

Denso supplies no information at all on the reach or gap of these plugs, none. No platinum was mentioned with respect to the IKH2x series of plugs, I'm assuming they are iriduim to steel.

Denso supplies the 2005 WRC Subaru team with a special plug. This plug has the iridium to platinum jump and has a more contained gap that is less likely to break, chip, dislodge, under hard racing condtions. Similar plugs made by Denso cost $35-40 per plug and are called "Denso Iridium Racing" plugs.

Common Plug Gaps Used By NASIOC Members

0.028-0.031 inches--from the STI factory manual (aka 0.7-0.8 mm)

0.028-0.029 inches--The "I gap'em 0.028-0.029 no matter what" school

0.044 inches--that's what the "-11" refers to at NGK -11= 1.1 mm = 0.044 inches

0.030-0.032--that's the real gap, even when the -11 means 0.044 inches

0.028 inches--"because it’s a good compromise for power and longevity"

So What's What

NGK Iriduim vs. Iridium IX-- appears to be difference in the ground electrode. The plain Iridium plugs (a la OEM plugs) have platinum tip on the ground electrode and hence they cost more. The aftermarket "Iridium IX" lacks this platinum tip--it's steel. So, the OEM jumps/sparks from 0.7 mm Iriduim to a small platinum patch. The aftermarket jumps from a 0.7 mm Iridium tip to a steel ground, no platinum patch. (You might ask why iridium at all, why not copper or platinum--it's mainly becuase its a pain in the butt to change plugs and people won't pay for "tune-ups" ever 10,000 miles--iridium lasts longer)

NGK vs Denso--people don't like the Densos for one of three common reasons: 1) the smaller iridium patch (0.4 mm) fouls more easily than the NGK's 0.7 mm patch. 2) the Denso's are more fragile, you can easily knock the iridium off of the electro-tip, this fragile-ness may extend to detonation fragility as well, 3) they don't like the company, new comer to plugs, whatever.
__________________________________________________ _____

OK, why write this long winded post? Well, I'm misfiring, and a lot of other people are too. Now this is not coil-pack-gone-bad-style misfiring. I can detect mine at a very specific RPM range in 4th gear. Between 5-6000 RPM my car will cut-out ever so briefly maybe 3-4 times. It does not back fire and really makes no sound at all (no boom, no spark and vice versa), but you can feel the acceleration loss/re-engagement and there is a momentary loss of the boxer belch.

I could very well be misfiring in other gears, and at other RPM, but I just don't notice it.

When my car was on the dyno, Phil worked hard on tuning out a mis-fire at 5600 RPM. He tuned it out, but it's back, and in a few other spots nearby. I've tried to tune out the misfire myself, but nothing has worked.

What Plug/Gap to Use?

We'll I don't believe the "one step colder" stuff anymore (great for 2 stroke scooters though). It might make a difference if you car is solely a track car, but for most of us we are just fouling our plugs earlier because they are not running hot enough in normal "off-boost" driving.

I think most of the plugs above will work without misfires if they are gapped to do so. What the gap should be is a highly debatable factor.

I do believe that 0.044 is too large of a gap for a turbocharged engine.

I would stick to the stock "temperature range," which is 6, unless you have a damn good reason to run colder plugs that is proven to assist in your detonation problem--note the words: proven and problem.

I think Subaru is in the best position to determine the gap, and they recommend 0.028-0.031. The smaller the gap, the more guarantee that the plug will spark and not misfire (not spark). The plugs wear faster the smaller the gap, but plugs wear really fast if there's no spark.

Gapping an Iridium plug requires either a special tool or a great deal of care. Even checking the gap should be done with great care. The iridium tip is fragile no matter what manufacturer you buy. None the less, you should check the gap of the plugs you purchase before you install them, I in IMHO they should fall into the Subaru spec, and be matched to the same gap for all 4 plugs.

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04-28-2005, 09:03 PM	#18
Unabomber Tom @ Kartboy's nemesis Join Date: May 2004 Location: Virginia Beach, VA Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts Groans: 0 Groaned at 0 Times in 0 Posts	Just changed the plugs in my car today. The advice offered here and on the other couple of spark plug pages is great. I will add that having a mid-well 12mm socket would help a ton. For you tool n00bs, mid-well is a newer socket style between a short one and a deep-well. I was cursing my buddies tool set for not having a mid-well. The need for it is apparent as you don't get enough engine clearance with a short socket and a deep one or short + small extension will give you too much and put you into the engine well. I made due with what my buddy had, but it would have been FAR easier with a 12mm mid-well socket.

05-08-2006, 10:09 AM	#20
Blk_RS01 Registered User Join Date: Apr 2006 Location: Charlotte, NC Posts: 4 Threads: 1 Thanks: 0 Thanked 0 Times in 0 Posts Groans: 0 Groaned at 0 Times in 0 Posts	I just changed out my plugs and wires today and.. for those who might not have tools.. advanced autoparts have this tool set for only 7 buck and it comes with the right sockets (with magnets inside them already/extensions and even a tilted wrench

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