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DIY: How to change spark plugs (3.0L V6)

294428 Views 234 Replies 116 Participants Last post by  Nolimits865
I swapped out my spark plugs today at 50k miles. The maintenance schedule calls for new plugs at 75k miles, but it also calls for things like never changing the transmission fluid. I was also bored needed something to do. I decided to go with the Autolite XP104 plugs. Overall, the process wasn't too bad, but it is definitely time consuming. It takes a little studying to figure out how the wiring harness mounts come off the Intake Manifold and this is by far the part that will cause the most problems for anyone. Enjoy:

1. Disconnect the negative battery terminal.

2. Hoses - There are 4 hoses total that need disconnected. 3 in the back of the IM, and 1 hidden under the throttle body. Use vice grips to squeeze, unclamp, and hold the hose clamps. I didn't see the hidden one until it came time to remove the IM, this may be when you need to remove it too. The hoses push right off with minimal effort.

3. Wiring Harnesses - Ensure your battery is disconnected. Disconnect the plug on the left, and the plug on the right. On the left, use a knife to carefully cut (or crumble) the tape which holds the harness to a post on the IM. On the right, use a knife (with new blade) to carefully score a notch around the mounting tab of the black plastic, 'box-like wire guide'. Keep scoring it until this wire-guide box separates from IM. Use a flat tip screwdriver to lift the white tab and slide each harness off the IM. Don't be afraid to move these harnesses around a bit.

4. Accordian/CAI - Disconnect the MAF harness. Remove the accordian, or angled hose for the intake. Push intake to the right, into its 'hole' a bit.

5. EGR - Remove the 3, 8mm bolts from the EGR bracket. You will probably need a 8mm box wrench for the one without clearance in the back. Do not drop bolts into the engine bay.

6. Throttle Body - Lift the red tab of the harness, and disconnect. Remove (or break) the harness mount from the IM. Start with either of the bottom bolts, and remove the 4, 10mm bolts from the TB. Do not drop bolts or washers into the engine bay. It is not necessary to disconnect the coolant hose from the TB, just push the TB off to the right.

7. Intake Manifold - These bolts stay locked in the IM, they do not come out or fall out. Use an 8mm socket with extension to completely loosen all 8 bolts. Observe how easy they feel when they break inital torque. Do not use a screwdriver with an 8mm nut driver tip. Once all 8 bolts are loosened, lift up on the IM. Move the right wire-guide box out of the way, and push the EGR off to the right to clear its tube out of the IM. Keep doing this while lifting and moving the IM off to the left, until it comes out altogther. Lay it on the ground, upside down ensuring the gaskets do not become dirty. Get an old, but clean towl, and lay it over the intake ports on the engine block...this will help avoid any sudden disasters. Latch the hood and take a break.

8. Spark Plug Removal - Open and close 1 at a time, and start with the fronts to get a general feel. Remove the 8mm bolt. Carefully pull on the plug-top, remove, and let hang. Try not to let the end touch anything dirty. Use a 1/2" drive socket, with 3/8" adapter, an extension of your choice, and the 5/8" spark plug socket. Be very careful, your block is aluminum. Insert the extension into the tube and lock the spark-plug socket onto the spark plug. Put your left hand over the joint of the extension/socket, and right hand on the handle. Slowly turn the socket CCW, as soon as you feel the initial torque break, stop, then slowly continue turning until you feel the spark plug become free of the engine. Withdraw the old spark plug. Keep track of which spark plug was in which cylinder, to observe any wear problems. All 6 of mine were lightly coated with white-ish carbon, which is normal wear. The tip was shorter though.

9. Spark Plug Installation - Observe that the set gap of the new spark plug is .044 with a gauge tool. Insert a new spark plug into the spark plug socket. Put a dab of anti-seize grease on the threadings, and spread it with a paper towl and your fingers. Insert the complete socket extension with spark plug into the hole, DEAD ON STRAIGHT. SLOWLY turn the the socket CW, ensuring its dead straight to avoid cross-threading. If it cross threads, the engine is done. The new spark plug should turn so smoothly that it feels like a hot knife through butter. When you feel it beginning to torque, stop. Carefully turn the the socket in 1/16th of a turn increments until it feels sufficiently snug. If you overtorque it, the spark plug may break, deep down in that hole...and your day will be ruined. Insert the plug top, and push it until it seats with the new spark plug. Replace the 8mm bolt. Repeat 8 and 9 for the remaining cylinders.

10. Replace the Intake Manifold - Replace the IM by inserting the EGR tube into the IM. Carefully work the IM into place by lifting on its locked bolts, moving the wiring harnesses around. Connect the hidden hose first. Finger tighten the 8mm bolts on the ends, and ensure the IM is lined up. The machined bolt hole tabs on the IM should match up perfectly with the machining of the block. Tighten down the 8mm bolts in a staggering pattern. Remember how they felt when they came loose, these do not need cranked down.

11. Replace the 3 back Hoses and Wiring Harnesses. Replace the left and right harnesses to the white tabs of the IM, and reconnect.

12. Replace EGR - Replace the 8mm bolts to the EGR bracket.

13. Replace TB - Position the TB against the IM. Replace the top 10mm bolts to the TB with fingers, then replace the bottom 10mm bolts. Tighten with 10mm deep socket. Reconnect the TB wire harness, then push the red tab down.

14. Replace accordian/CAI. Reconnect the MAF harness.

15. Check over all your hoses, and wiring harnesses. Make sure everything is re-connected. Reconnect the negative battery terminal.

16. Wash your hands, start the car, and observe for any weird behavior or noise. If it starts, then immediately stalls, check your un-connected MAF. WAIT...disconnect the negative battery terminal first, reconnect the MAF, then reconnect the negative battery terminal. I almost plugged in the MAF while still powered, but I caught myself. Take it for a test drive in a safe, known area. :drive: It should feel perfectly fine. You just saved yourself a couple hundred bucks.

I haven't noticed any particular differences with the Autolite XP104, although the engine seems to have a more aggressive and perkier startup. I haven't been able to hammer on the throttle yet either though.
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which coils did you use?
So the IM, EGR,and TB gaskets are reusable right? I'm changing my plugs on Sunday. i already got the AP104's, gapped today at .055
ok thanks, im about to tackle this tomorrow morning.
Spark plugs are done! The 6 is back!
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Anyone have the pdf file created earlier in the thread for changing the plugs, the link is not valid anymore
Thanks in advance would really appreciate it
were you looking for pics specifically?

this may be the hardest part, but just take your time, no rush!
pcv if you havent yet
autolite AP104 plugs are cool. they have some platinum, but not too expensive and they are good plugs for a stock setup. pcv (positive crank case ventilation), it twisted clock wise in to the rear valve cover, a plastic tab secures it until it is removed, by twisting the pcv in the opposite direction. a pair of long needle nose pliars will help remove it(counter clock wise)
oem motorcrafts
did you change ur plugs on your 6?
no, i havent changed mine since my last post....2.5 hours aint bad! im still trying to figure out which coil(s) is going out. i went to a couple auto parts stores for diagnostics, but no check engine light(CEL)=no luck.
how does it run now? was it misfiring/hesitating before you changed the plugs? mine ran much better the 1st week after changing my plugs, but my symptoms returned, which is why i'm looking to replace my coils next...prob 3 at a time
how ya been? no not yet, u change yours since the get together?
i would help you do yours but i guess Shel got you since he's not too far.
which plugs did you use? put money aside for coils too. trust me they're next about $45 ea at O'reillys Auto Parts store, maybe the cheapest besides ebay
o cool, i didn't know they'd work well on the 6. i heard bad things but maybe someone didn't install something correctly
ok, sounds good. it'll be good to know that we have more options w/o problems
i just bought the original motorcraft spark plugs and gapped them to .055, the book specs-.051-.057
ill try to take pics for people who havent tried
3 quick videos

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i hope the short videos give some sort of visual to page 1 of this forum. i wish i could've recorded the whole thing, but i didn't have a camera man and i can't multi-task. it's running fine, i also tested m coils and they seem fine, but who knows.
great work, i never really kept up with my mpg in my6. all know is i get around 300 miles before i fill again(87octane). im considering the egr re-route on my car soon, i didnt do the old "egr mod". i rather have fresh air coming in!
o yea, i checked 3 of my coils last night and one them was cracked at the top of the housing, near the connector. it was soooo thin, like hair. all this time, i had been looking at resistance and the coil boots...i was so desperate to find the problem, i took the boots off the coil, to check the spring like part inside. well, i know how to check the other three now!
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