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While searching for info on spark plugs (e.g. platinum vs iridium, Denso vs NGK) I noticed that there were quite a few members asking about how to change their spark plugs, but there didn’t seem to be any write-up on the subject.

Having just purchased 8 NGK Iridium IX plugs (part # 6418) and a K&N air filter (part # 33-2144) I decided to do my own write-up. If there is already one out there my mistake.

Note that this how-to is specifically about the Toyota 4.7L V8 (2UZ) engine; however the steps are basically the same for most engines. Changing all 8 plugs in this engine will take an average of approximately 1-2 hours, depending on your ability, how anal you are (me as I get older) & the amount of beer being consumed (me not too many years ago). In my experience & opinion this has to be one of the easiest engines to change plugs.

Personally, I prefer to work on a cold engine, but if the plugs you plan on removing are seized (stuck in place) you may want to run the engine for a little while to hopefully expand the metal and possibly make it a little easier to twist them out.

The basic tools you will need are:
- socket wrench
- 10mm socket
- socket extension (6-inch works great)
- 5/8inch spark plug socket (a dedicated deep socket that has a rubber boot inside that “grabs” the spark plug so you can easily pull the plug out)
- spark plug gap tool


The following is great to also have:

- torque wrench
- anti-seize lubricant
- dielectric grease
- compressed air

I recommend to the spark plug changing virgins, to do the passenger side spark plugs first since the driver side has cables and hoses that have to be worked around. Note, however, that these pictures are taken on the driver side because I wanted to use the oil dipstick as a reference point.

See the yellow oil dipstick in the below picture? The red arrow is pointing to the wire harness that connects to the top of the ignition coil; green arrow is pointing to the ignition coil; blue arrow is pointing to the ignition coil retainer bolt.


Before proceeding use your compressed air to blow any debris away from the engine area you will be working on. Next, press the retainer clip on the wire harness (pink circle in picture above) and at the same time slide/pull the wire harness up and away from the ignition coil. Be sure not to pull on the wires because you do not want to accidentally pull them out of the harness.

Next, with the wire harness moved out of the way, use your socket wrench and 10mm socket to remove the retainer bolt (blue arrow below).


With the retainer bolt removed you should now be able to easily pull the ignition coil out of the cylinder head.


Now you can look in the cylinder head and see the top of the “old” spark plug down inside.


Before proceeding now is a good time to use your compressed air again and blow out any debris that may be in the hole down around the spark plug.


If you haven’t already, these particular spark plugs (NGK Iridium IX # 6418) for this particular engine are to be gapped at .032inches (per NGK). NOTE that since this write-up was initially created an important point was brought up by forum member "Mantion". I have added the following for explanation/information... NGK's FAQ to gapping these Iridium plugs is found HERE (NGK website). Also note that despite the caution of gapping these plugs, they do provide the proper gapping settings HERE (NGK website).


A look down the dedicated spark plug socket (notice the rubber boot ring inside).


If you only have a standard 5/8inch deep socket (no rubber boot ring) then you better have a magnetic stick otherwise getting the old spark plug out will be a PITA or a feat of clever engineering.

With your new plug properly gapped, now is the time to apply your dielectric grease to the top of the new plug (orange arrow) and the anti-seize lubricant to the threads of the new plug (grey arrow).


The reason why I think you should apply your grease & lube now and not earlier is there is less chance any dust will attach itself to the goo. Adding to that, I think that adding the goo right before you get the old plug out lessens the chance of debris falling into the cylinder while you have the old plug out and a big hole sitting there. Anyway, now is the time to attach your 5/8inch spark plug socket to your socket extension and using your hand fit the socket onto the old plug and make sure it is all the way on. TIP: because there is limited space to move around, by not having the wrench already attached you’ll have an easier time getting the socket to fit on the plug.


Now attach your socket wrench to the socket extension and remove the old spark plug in a standard counter-clockwise motion until you feel it release - and just pull the socket assembly up and out comes the spark plug held to the socket rubber boot ring.

Pull out the old spark plug and insert the new spark plug into the same socket you just took the old spark plug out of. If you’re using dielectric grease, be sure to center the spark plug as you slide it into the socket so you don’t smear the grease.

Remove the socket wrench so you have just the new plug in the socket with the socket attached to the socket extension. The reason for removing the socket wrench is it will be easier to properly seat the new spark plug threads when you go to twist in the new plug. Using your hand carefully twist the socket extension in a clockwise motion so the spark plug screws into the cylinder head properly. TIP: although it is relatively difficult to cross-thread a spark plug, an easy way to be sure the threads line up is when you have the plug all the way to the bottom, slowly turn the socket assembly counter-clockwise feeling for the thread notch - then begin threading it clockwise like normal. Continue threading the spark plug with your hand in a clockwise motion until it is “hand tight”.


Next, attach your torque wrench to the socket extension and tighten to 13ft/lbs.


Next slide the ignition coil back down and press onto the spark plug. Add the ignition coil retainer bolt and tighten to 5.5ft/lbs. Last step is to reattach the wire harness clip to the top of the ignition coil. Make sure you hear the “click” sound.

Repeat the above steps for the remaining 7 plugs. Happy wrenching!

Ben
 
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very nice, thank you for taking the time to do this! not everyone has a ton of auto repair experience so i'm sure this post will be helpful to many.
 

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If anyone can cite the proper torque settings (for the plugs and the ignition coil retainer bolt) and the reference from where you got your torque info it would be appreciated. Please no guesses, I already did that. :tu:

Ben
13 ft-lbs is the correct torque for dry spark plug threads. With an anti-sieze lubricant which reduces friction it's a good idea to reduce the tightening torque to about 10 or 11 ft-lbs.

The tightening torque for the coil pack bolts is 66 in-lbs (5-1/2 ft-lbs). Source - Toyota Factory Repair Manual, page SS-19.

I don't bother to disconnect the wire harness(es) from the coil packs - the harness(es) is/are long enough that this is not necessary.

You applied the anti-sieze too far down the spark plug threads. The first full thread should be dry so that no anti-sieze ends up inside the combustion chamber. I doubt that this is much of a problem though.

When torquing the spark plugs - or anything else for that matter - it's good practice to hold the head of the torque wrench with your free hand. This prevents the head of the wrench from moving sideways - cocking - and makes sure you get an accurate torque.

I don't think the dielectric grease is necessary. Remember, the dielectric grease is not an electrical conductor, it's an electrical insulator. Its purpose is to prevent corrosion of electrical connections by preventing water or moisture intrusion. This is a good idea for, say, license plate bulb sockets, but the spark plug boot gets baked every time you run your engine and the rubber gasket at the coil pack effectively seals off the spark plug tunnel. There are zero problems with water intrusion or corrosion at the spark plug connector.

It's my opinion that the best plugs for the 2UZ-FE are the basic copper plugs specified by Toyota. For my 2004 Sequoia that's part number 90919-01166 (DENSO K20R–U). There are no performance or fuel economy gains with the expensive plugs.

It's also my opinion that K & N air filters are a bad idea. They are poor air filters that allow a lot of silicon (dirt) to enter your engine. The factory air filter is not restrictive and can be left in place for much longer than the factory service interval - 50,000 miles or more. A dirty air filter actually filters better than a new air filter and does not affect fuel economy on modern vehicles like the Sequoia with closed-loop Air-Fuel-Ratio control.
 

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Discussion Starter #5
where'd the photos go?
I don't know what happened to the original images. Had to redo them even though they were all still in the photobucket account - strange.
 

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Discussion Starter #6
13 ft-lbs is the correct torque for dry spark plug threads. With an anti-sieze lubricant which reduces friction it's a good idea to reduce the tightening torque to about 10 or 11 ft-lbs.

The tightening torque for the coil pack bolts is 66 in-lbs (5-1/2 ft-lbs). Source - Toyota Factory Repair Manual, page SS-19.

I don't bother to disconnect the wire harness(es) from the coil packs - the harness(es) is/are long enough that this is not necessary.

You applied the anti-sieze too far down the spark plug threads. The first full thread should be dry so that no anti-sieze ends up inside the combustion chamber. I doubt that this is much of a problem though.

When torquing the spark plugs - or anything else for that matter - it's good practice to hold the head of the torque wrench with your free hand. This prevents the head of the wrench from moving sideways - cocking - and makes sure you get an accurate torque.

I don't think the dielectric grease is necessary. Remember, the dielectric grease is not an electrical conductor, it's an electrical insulator. Its purpose is to prevent corrosion of electrical connections by preventing water or moisture intrusion. This is a good idea for, say, license plate bulb sockets, but the spark plug boot gets baked every time you run your engine and the rubber gasket at the coil pack effectively seals off the spark plug tunnel. There are zero problems with water intrusion or corrosion at the spark plug connector.

It's my opinion that the best plugs for the 2UZ-FE are the basic copper plugs specified by Toyota. For my 2004 Sequoia that's part number 90919-01166 (DENSO K20R–U). There are no performance or fuel economy gains with the expensive plugs.

It's also my opinion that K & N air filters are a bad idea. They are poor air filters that allow a lot of silicon (dirt) to enter your engine. The factory air filter is not restrictive and can be left in place for much longer than the factory service interval - 50,000 miles or more. A dirty air filter actually filters better than a new air filter and does not affect fuel economy on modern vehicles like the Sequoia with closed-loop Air-Fuel-Ratio control.
Thanks for your constructive comments, especially the torque settings. If it wasn't obvious, this write-up was intended for the forum members that are not experienced in turning wrenches.

Therefore, disconnecting the wire harness from the ignition coil is going to help the first-timer when trying to pull the ignition coils out on the driver side because of all the ancillary hoses and wires.

Also, I took a picture of the torque wrench with my only free hand, if I had three hands I would have had one on the head of the wrench, as I did in application, and my third hand holding the camera ;) But good pointing that out as the picture may suggest otherwise. Hopefully common sense takes over and the user notices the torque wrench wobbling and holds it with their other hand.

Correct about the dielectric grease. However it does not inhibit the connection in any way and is a simple preventive measure that I think is important for a first-timer. On these engines the likelihood of water getting down there is slim, but is not the same story on other engines for other vehicles.
 

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AAAAAAHHHHHHHHH, DON"T GAP IRIDIUM PLUGS, Please, please, please remove that step...

Great write up, but again, please remove that step, Iridium is very hard, and very brittle, I don't know of a single Iridium plug that is supposed to be gapped, it is way to easy to snap the ultra thin core.

BTW, I put Iridium plugs in my 2003 Sequoia about 3 years ago, took out 7 of them and they look good. I haven't seen any increase in performance and my millage appeared to drop after. I think it is back up, perhaps the computers had to adjust for the new plugs.
 

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Discussion Starter #9
AAAAAAHHHHHHHHH, DON"T GAP IRIDIUM PLUGS, Please, please, please remove that step...

Great write up, but again, please remove that step, Iridium is very hard, and very brittle, I don't know of a single Iridium plug that is supposed to be gapped, it is way to easy to snap the ultra thin core.

BTW, I put Iridium plugs in my 2003 Sequoia about 3 years ago, took out 7 of them and they look good. I haven't seen any increase in performance and my millage appeared to drop after. I think it is back up, perhaps the computers had to adjust for the new plugs.
I gapped them because they were not gapped to the proper gap, per NGK. However, I think you bring up a very good point :tu: and have edited the post as such.
 

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Nice write-up, I replaced the plugs on ours with 120k today, and I am surprised it even ran as bad as they looked. I also replaced the fluids in the diffs and transfer case.
 

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Anyone have trouble getting their original plugs out? My '05 Sequoia has 167000 km (104000 mi) and I'm worried about breaking a plug.
The ones in our '02 with 85K came right out. A couple complained a little but I highly doubt you will snap them.

Worst come to worst if they start to really creak or feel like they are going to snap, turn them a turn or two back in the tighter direction and then back them out again. It helps, believe me.
 

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I did plugs on my 2004 Seq Ltd with 98,000 a month ago. I think it still had the original Denso plugs in it and they were in pretty bad shape - one of them had signs of some blow by.

I put the NGK iridiums back in - they were gapped perfect out of the box - .32 from memory. Not sure about the gapping discussion from earlier posts. FYI I just pulled a similar NGK iridium plug out of my Lex LS400 (1UZFE engine) after putting 105,000 miles on them. The plug was in great shape and only a few hundredths out of gap after 105lk - .47 compared to .44 from memory again. I'M glad I didn't wait any longer. A couple of them were really in there and I took care to torque them to spec 5 years ago. I was pleasantly surprised at how well they held up to that kind of mileage but for corrosion and sticking purposes don't wait longer than 100k. I did use a little never seized on these years ago. Just my two cents.
 

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Perhaps putting a little penetrating oil into the spark plug hole and allowing some time for it to seep into the plug could help.
 

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gap should be .44 with the DESNO branded iridium plugs- my new DENSO SK20R11 plugs DIDNT come gapped right, so I properly gapped.

When I removed the factory NGK plugs, they still looked decent at 114k.

I just did this job this weekend- probably easiest plug change Ive ever done except the drivers side rear is kinda tight with hard fuel lines

plugs.JPG plugs.JPG
 
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