Subaru Forester Owners Forum banner
1 - 20 of 237 Posts

· Premium Member
2022 Forester Limited 2018 Forester XT
Joined
·
16,590 Posts
Discussion Starter · #1 · (Edited)
N/A Spark Plug Replacement

Yes I am extremely anal when it comes to this stuff.

First Impressions:
1. First time is gonna' be long
2. Do the passenger side first bc after you remove the air filter housing..room is abundant. This will make it easier and make the driver side easier (for your first time).
3. Remove the air filter housing. Although I removed the Battery . it is NOT necessary
4. Changing plugs at 30K miles is nowhere necessary. But its good to do bc they will come out easier next time.
5. Have two 3" extensions ready on the driver side. You need to put the socket in in two steps (probably)
6. Do the job when the engine is cold.
7. Be prepared for a skinned knuckle or two
8. Its unlikely you will be able to use a torque wrench on the driver's side. Passenger's side probably you will be able to use one.

I have done several dozen plug changes in 45+ years and I would rate this as a '6' or '7' difficulty comparatively.

WRITEUP

Tools:

1. 5/8" Spark Plug Socket
2. two 3" extensions. (Driver side)
3. 8" to 10" extension (Passenger side).
4. Short handle ratchet (especially for driver's side)
5. 12 mm socket (Air Filter Housing hold-down bolts)
6. 8mm socket (Hose clamp -Air filter Duct to Housing)
7..Duct tape (Taping extensions/socket together)
8..Sharp Knife (Cutting away Duck Tape :) ) (or slashing your wrists-j/k)
9. Rubber Hose (Sucking/blowing debris out of spark plughole)
10. Anti-seize (Plug Thread * )
11. Dialectic Silicon Gel (Plug boots/Plug insulator)
11. Various Cleaning Supplies, flashlight, mirror, bandages, Whiskey, Beer, etc.
12. New Plugs
13. Ohm Resistance Meter (Optional)

Procedure:

* Gather up all tools ahead of time..make sure you are in the mood for this job.
* Do passenger side first.
* Insure car is cold.
* Remove air filter element
* Break connection where duct hose engages filter housing.
* Duct Tape upper filter housing toward the the fire Wall (so its out of way)
* Remove Lower bolts for lower filter housing (two- 12 mm). 10" extension is nice here.
* Housing may stick to lower mounting bolts-break free.
* Pull lower housing away from fender (air inlet) - remove from compartment.


* This is what you should be dealing with:



* Loosen guides for spark plug wires so you have flexibility in the wires.
* Grab the rubber handle on the boot and attempt to rotate the boot say 45 degrees in both directions.
* I'm not really sure rotating breaks it free at boot. Might be a waste of time.
* DO NOT PULL ON WIRE !
* Grab Boot at handle or anywhere except wire and Pull like hell..It may be ugly. :(
* Take piece of rubber hose, insert in hole and blow out debris.
* Tape 5/8" socket to 10 extension and put in hole and engage plug. (Insure you are engaged.



* Break Plug free and loosen very slowly. If it sticks go count clockwise and then counterclockwise in small increments
* Someone previously indicated spray brake cleaner for sticking plug (with extension spray tube).
* Remove plug, use hose to again blow out hole.
* Clean threads on old plug, lube with anti-seize* and run totally home using hand (no wrench)
* Lube new plug anti-seize* and use dialectic liberally on insulator.
* Run plug totally to seat using no wrench. Insure several times that it is seated.
* Torque to spec. (15.6 lbs) I used less ...(11 ft. lbs) With Anti Sieze
* The manual says to use 1/3 less torque when using anti-sieze. So that's about 11 ft. lbs
* The the correct torque will be 1/2 of a turn ( MAX) after "hand" contact
* Lube around housing and boot seal with dialectic.
* If you are going to check Resistance in Plug wires do it now
** Should be 9 to 16 Ohms. Use dialectic when reinstalling boots on supply end of wire.
* Push boot on plugs and 'feel' engagement.
* Repeat with other Plug.
* Reinstall Air filter Housing and filter.

*** Driver's side: (Battery removal not necessary)



* Utilize 3" extensions..tape one extension to socket.
* For removal, if extensions come apart its not a big problem you can push them together even if in hole.
* For installation, it the socket sticks to plug and the extensions come apart. You may need to:
*** Remove plug or
***Put a hook on a piece of wire and hook the pieces out (I needed to do this)
* Its unlikely that you will be able to use a torque wrench. Develop feel on Passenger Side ones. ( approx just about 3/4 turn after hand seating)

Other suggestions/Problems:

* Do two plugs and test drive, After cooling, do the other two,
* I didn't intend to do the job but after I pulled 2 plugs I went and bought Autolites bc NGK not available. Second time used NGK
* There is controversy about using anti-seize. I used it this time. I used 11 ft lbs with a small bit of anti-seize but later found: (from Subaru) Use 1/3 less torque with thread lubricant..11 ft lbs
* If you disconnect the battery, vehicle will not start on first try. Should start on second try.


If anyone thinks of other things, I'll add them

Oh..here's how the plugs looked after 31K miles

 

· Registered
2005 Impreza RS Wagon Auto
Joined
·
4,630 Posts
I took the windshield washer reservoir and pump out to make the driver's side much easier (still not easy though). Took me one hour first time.

Would you recommend getting your oil tested every time yo do your plugs by blackstone? haha...
 

· Registered
Joined
·
730 Posts
The battery can stay in but the windshield washer reservoir must come out. It helps if the thing isn't full to the top too.

A mechanics stick magnet works great if your spark plug socket doesn't hold the plug tightly and the plugs want to slip out. Just unthread the plug all the way, remove the socket and fish the plug out with the magnet.
 

· Premium Member
2022 Forester Limited 2018 Forester XT
Joined
·
16,590 Posts
Discussion Starter · #7 ·
I took the windshield washer reservoir and pump ou
Would you recommend getting your oil tested every time yo do your plugs by blackstone? haha...
Not close to being needed on the 2008 (Windshield washer). 'No' on the oil analysis unless there is a problem. But maybe not a bad idea.
 

· Registered
2004 Subaru Forester XT 5 speed manual.
Joined
·
795 Posts
Nice write-up. Doesn't sound too hard, just time consuming!
I'd also recommend wearing mechanic's gloves for the super tight spots.. so you don't skin your knuckles. :)
 

· Premium Member
2022 Forester Limited 2018 Forester XT
Joined
·
16,590 Posts
Discussion Starter · #14 ·
Great Pics! Thanks so much! I'm going to try and do it myself next time!
You are welcome. If it helps one person, it was worth my time.

As much as I was leaning on letting the dealer do the job and being I'm 63 and getting tired of this crap..... I just know that I would do the job better than some wrencher at the dealership..
 

· Administrator
2007 Forester Sports XT 4EAT
Joined
·
44,111 Posts

· Registered
2004 Subaru Forester XT 5 speed manual.
Joined
·
795 Posts
Rep given as well. I have a multimeter that I haven't really used yet. What would be the best way to check the spark plug wires for ohm resistence?
 

· Premium Member
2022 Forester Limited 2018 Forester XT
Joined
·
16,590 Posts
Discussion Starter · #18 ·
Rep given as well. I have a multimeter that I haven't really used yet. What would be the best way to check the spark plug wires for ohm resistence?
Just select the OHM scale and put the leads at opposite ends of the wire. You need to remove the wire from the car.
 

· Registered
2015 Forester X 6MT 6-Gear Manual
Joined
·
1,378 Posts
ADC, Nice writeup.
The only thing that gave me a problem in the past is too much dielectric grease on the boot(s). I've backed off to the point that I just skim the inside if the boot with my pinky finger. The Tip Connector doesnt like the grease - though in theory it shouldnt be a problem. I clean the boots inside and out using ethanol mixed with a tiny bit of distilled H2O. Plug boots dont like salt from the road OR from your sweaty palms; it only takes a little to migrate and cause a high misfire count in humid weather. Same goes for the plug socket insulator. It shouldnt transfer dirty grease onto the plug insulator. I usually weAr clean latex gloves to handle the new plugs, then thread the plugs in with a piece of fuel hose then tighten without the plug socket rubber insert. Another biggie - normal folks dont understand high-tension wires and what they like and dont like; but they surely DONT like to be under strain or torsion; so let them droop naturally the way they want to hang and try to keep that orientation when you re-insert the boot. Add these hints to your tune up list and you should have a car that runs BETTER after a tuneup other than worse. BTW, these are some of my SCCA racing secrets for extra HP, so dont tell anybody;)
 

· Registered
2015 Forester X 6MT 6-Gear Manual
Joined
·
1,378 Posts
I remember my first time.. stupid H.. wished this was a V engine! LOL real lyte..
But NOT a twin turbo mitsubishi V6. You couldnt drop a marble under the hood and have it come out on the road or belly pan. Had to remove the intake manifold and FI to change the back bank 3 plugs:icon_eek:Here's a pic of the NA engine which has a little more room:
 

Attachments

1 - 20 of 237 Posts
Top