How-to: DIY Spark Plug and Intake Plenum Gasket Replacement

TheFauxFox

Titan Swapped / SAS'd
Founding Member
Location
Huntsville, AL
With a lot of forum posts dropping like flies due to Photobucket’s new policies, a new How-to needed to be posted for changing out spark plugs on your newer model Xterra, Frontier, or Pathfinder. Preliminary acknowledgements go to rouguebuck on TNX who had the most complete write-up I found.

First and foremost, you can do this. It will take about 1-3 hours depending on your beverage intake and your mechanical knowledge. I recommend having the right tools for the job (and not living in hotter’n heck Abalama).

Before we get started, I want to note that I started on the passenger side since this side requires the removal of the intake plenum and I knew it would take significantly more energy than the driver side.

I was not wrong.

Parts Required:
-Spark Plugs (I used NGK Iridium LFR5AIX-11) (6x)
-Dielectric Grease
-Upper Intake/Plenum Gaskets (Set of 3x)
-Engine Oil (opt.)

Tools I Used:
-Phillips head screwdriver
-Flat head screwdriver
-12mm box wrench
-10mm box wrench
-1/4” socket wrench
-3/8” socket wrench
-10mm deepwell socket
-12mm socket (and/or deepwell)
-5/8” [16mm] spark plug socket (or similar, standard deepwell)
-9” of extensions for 3/8” socket wrench
-Needle-nose pliers

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1) Locate your engine and remove the pretty stuff.
You can do this, right? Yours may not look like this one because of the K&N intake. Remove the two 12mm bolts on the “V6 4.0” cover Remove the two bolts connecting your intake tube-to-air cleaner box to the “V6 4.0” cover. Gently pry up the cover. They’re on pretty snug, but aren’t retained like the stupid pop-rivets that hold on trim, so don’t be afraid to pry. Prying from the passenger side first was a little easier.

Also, loosen the hose clamp(s) that connect the air tube to the throttle body and separate the two. This can be done with a screwdriver or a 10mm.

Oh, and remove the negative side of the battery unless you gangsta. I’d rather you not fry yourself or anything else. I don’t like the zap-zaps.

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Figure 1. The Engine Bay

2) Remove vacuum connector and the canister.
This little canister needs to removed for a later step. Remove the two-pin, gray connector. Then remove the two bolted components. The canister is mounted with a 12mm and the adjacent bracket has a 10mm.

Also, start keeping a count of the number of electrical connections and number of hoses you disconnect. This will make it easier to remember at the end.

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Figure 2a. Vacuum Electrical Connector

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Figure 2b. Vacuum Bolts (Top is 12mm, Bottom is 10mm)

3) Removing electrical connectors and hoses from the throttle body.
Start by removing the larger connector located on the right of the throttle body.

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Figure 3a. Throttle Body Electrical Connector

Then remove the hose that goes up and over the throttle body. NOW, the FSM wants the mechanic to drain the coolant from the engine prior to starting. If you’re following that manual and this DIY, remove the hose connected to the bottom of the throttle body as well. OTHERWISE, DO NOT REMOVE THE LOWER HOSE. Now is not the time to be thinking, "screw what the guy with the pony picture says." I did not remove the hose.

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Figure 3b. Hoses Leading to Throttle Body.

4) Remove electrical connectors and hoses from the intake.
This is where the pain begins. Embrace it. You love your truck. You love your truck. You love your truck… at least you think so, right?

There are 2 hoses, 1 electrical connector, and 3 conduit retaining pop-rivets connected to the back of the intake. Take your needle nose pliers and slide the clamps away. My hoses were a little stuck on there. Push them further onto the nipple of the intake and then attempt to pull and twist. The first hose can be accessed on the passenger side of the engine just after the throttle body. The second line is tucked back there pretty far. Refer to the Figure 4C below.

As for the connectors, there will be a gray plug on the very back near the firewall. Go ahead and remove the plug from the bracket by pushing down on the little tab in the bracket, then slide it right. While your back there, push out the 3 pop rivets on the thick line of conduit. Those wires are stiff and will get in the way later. I had to cut the one on the far left.

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Figure 4a. Passenger Side of Intake

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Figure 4b. Pop-Rivet-Thing

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Figure 4c. Locations of Pop-Rivets (Arrows), Electrical Connector, and Rear Hose

5) Unbolt the intake/throttle body bracket.
This is located on the left side directly below the intake and throttle body and directly next to THAT HOSE I TOLD YOU NOT TO REMOVE. Its held on by two 12mm bolts. I had to use a box wrench on the first one, but could get a socket on the rear. These were on tight, so if you notice in the original tools list, I didn’t list the 15mm wrench. I used that wrench for the double-box wrench pry bar trick to break these loose.

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Figure 5. Throttle Body Bracket

6) Remove the 5 bolts and 2 stud-nuts from the intake.
Refer to the re-installation picture below for the location and order of reassembly (arguably disassembly) of each bolt/stud. Numbers 4 and 5 are the nuts. I don’t know what the issue Nissan has with the number 6, but that sucker is a little bit difficult to get to.

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Figure 6. FSM Intake Assembly Diagram
 
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TheFauxFox

Titan Swapped / SAS'd
Founding Member
Location
Huntsville, AL
7) Remove the intake.
Start by lifting up wherever you can grab it to break the seal a little. Then you really have to finagle the thing up and towards the passenger front. Be super careful to not pull to hard and yank some connections away. Once you get it free from the two studs, carefully swing it clockwise and rest it over the radiator. Remember that little coolant line under the throttle body THAT I TOLD YOU 3 TIMES NOW NOT TO REMOVE? Yeah, thats is why we’re just going to swing it. Just be careful not the yank or sever it. Once moved, plug or cover the intake ports.

Honestly, I had to stand on my steel bumper and sit nearly on the radiator to get the leverage I needed to do this. This was a curse and blessing considering I’m short and the bumper hoops really restricted my reach over the engine.

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Figure 7. The Swung-away Intake

8) Replace the intake gaskets.

roguebuck says it the best.

“I have seen plenty of internet engineers skip replacing these. I dont F@#$ around, so I follow the FSM. Just replace them, you already have the intake off.”

The come out very easily by pulling on the little tabs sticking out of them. Mine are brownish, but if they’ve been replaced, they could be black, blue (Felpro), or just like these. Some people say to use engine oil on these upon reapplication. Felpro specifically says not to add anything to theirs, which is what I bought, so I didn’t. They say that there is already a coating on there and any “unknown” substance may foul it.

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Figure 8. Location of the 3 Gaskets to Be Replaced

9) Remove the 10mm bolt(s) on the coil(s).
Seen as the yellow-zinc plated hole below, remove the 10mm bolt there and pull the coil out. I didn’t feel the need to remove the electrical connector, but if it behooves you, feel free to do so. It definitely would have made it a little easier to pull the coil out. Hang or place out of the way somewhere clean.

Here, I’m going to give you the option on how you want to do this. Skip this little bit of text if you want the fool-proof method. Otherwise, using some tape and a marker, mark each of the coil wires and label them in accordance to their location on the engine block. It really doesn’t matter in what order your label them as long as they’re all marked on the wire and location on the block. By doing this method, you can save yourself the time of removing and replacing the 10mm and spark plug socket every time you move to a new one. I didn’t ‘do this, but I also did this with the intention of doing this write-up. I’m also forgetful.

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Figure 9. A Removed Coil

10) Remove the spark plug(s).
Guys, we’re finally here. Using a creative collection of extensions and a socket, start removing the spark plug(s). I had to use a 3”, 6”, and 5/8” spark plug socket to get the proper depth. They’re in there very deep. I highly suggest you get a spark plug socket for the extraction and reassembly. The socket has a little rubber seat that helps grip it and retain it in the socket once unthreaded. Obligatory new/old picture.

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Figure 10. New vs. Old Plug

11) Inset the new plug(s) and reassemble the coil.
Once removing the plug from the box, apply some dielectric grease (silicone based) along the white part of the plug being extra careful not to apply it to the ends. Previous works have suggested the amount equal to the size of a single grain of rice, which has been the best quantifiable amount I’ve ever read. I’ve also seen some varying opinions on this next step. I applied engine oil to the threads of the plug, again, doing my best not to allow any of the oil to get to the tips. Others say to either apply anti-seize or nothing at all, since that’s what the factory apparently does.

Once you’ve lubed the shaft, shove the plug into your special spark plug socket and make sure its seated straight. Then without the socket wrench, insert the plug, still connected to the extensions, into the hole. Tighten by hand until firm. Confirm this with a light twist on with the socket wrench. Torque the plug to 18 ft-lb. If you don’t have a torque wrench, give it a 1/4-1/2 turn to completely seat the plug.

Push the coil back onto the plug until you feel the light pop of the boot seating itself on the plug. Put the 10mm bolt back onto the coil and torque to about 4-5 ft-lb (FSM says 62 in-lb).

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Figure 11. Putting in a New Plug

11b) Replace the driver side plugs as well.
I was on a roll, so I went ahead and replaced the driver side as well. You can do this before this whole ordeal or after. The intake really isn’t in the way nearly as bad for this. I chose to do it here anyway.

12) Reassemble in reverse order.
I hate telling people to do this, but it prevents me from having to write “do this, but now backwards.” I’m lazy. Be sure to install the intake following the tightening pattern below. Those bolts should be torqued to 8 ft-lb each. Don’t crack your intake.

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Figure 12. FSM Intake Assembly Diagram

Reassemble and such. Make sure you’ve reconnected everything and then reapply the negative battery cable. Start’er up. Some lights will remain on until you take it for a short spin (I’m talking to you little VDC POS). There should be no CEL/SES lights.

Congrats, you’re done. I told you it could be done.
 
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westslope

First Fill-Up (of many)
Terrific write-up indeed. This is on the near-term agenda and the how-to will be very helpful.

Am not sure if I will remove the plenum -- many do not -- but others do because it makes a) replacing the spark plugs easier and b) affords an opportunity to clean some of the gunk out of the plenum.

This write-up makes removing plenum and replacing the gaskets seem like a much less daunting task. If cleaning the plenum and replacing the gaskets promises to result in noticeable performance improvements, that would decide it for me.

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

I read here and elsewhere that two spark plug choices are very popular:

1.) NGK 6240 Laser Platinum (OEM) and OP TheFauxFox's choice.

2.) NGK 4469 Iridium IX

The OEM plugs are more expensive yet the Iridium IX plugs are estimated to last 1/3 longer than the OEM ones.

A number of apparently competent and experienced posters here and on theNewX.org have apparently purchased the Iridium IX plugs so that is what I will do. I know, I know.... lame authority argument.

Frankly, I suspect that both plugs are great plugs and the typical X owner would not notice a material performance difference in a proper test. If that is indeed the case, then why do the OEM plugs command a higher price? Smaller production batches? Large numbers of customers who absolutely insist on OEM components? Platinum is simply that much more expensive?

Just curious. Bit of a student of pricing strategies.
 

westslope

First Fill-Up (of many)
A big thank you to Thefauxfox as this thread was very helpful when I switched out the spark plugs and cleaned the plenum in late March 2021.

I did things a little differently. I wanted to detach the plenum/intake manifold collector so I could clean it. So I removed the electric throttle control actuator. That way I did not have to remove the anti-freeze coolant hoses attached to the throttle body actuator.

I also made a few mistakes. More on those later.

This YouTube video helped: How to Replace Spark Plugs on a 2005-2016 Nissan Xterra/Frontier with 4.0L Engine

From EM-17 of the 2006 FSM:

IntakeManifoldCollectorEM-17.jpg

The bolts holding in the electric throttle control actuator are hex bolts. I used an Allen wrench to remove and replace.

I sprayed brake cleaner and let the plenum soak for a while before scrubbing it with a flexible bristle bottle washer. Rinsed with citric-based cleaner and then rinsed thoroughly in the backyard with the hose. Took a while to dry.

The Fel-Pro gaskets fit well:

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There was a single oblong gasket with the Fel-Pro kit that did not look it would fit the electric throttle control actuator but it did. See below. (Not sure why it is not bright blue.)

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The plugs were worn and past due. I should have done this a while back...... I replaced with NGK Iridium IX 4469 spark plugs.

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I stripped a bolt and broke a couple of others due to literally using a cheap torque wrench and probably being rushed because an impending steelhead trip was coming up. I overtorqued the #3 ignition coil bolt and then used loc-tite to attach it. I snapped off the #3 bolt that holds down the intake manifold collector. Same for an air duct and resonator bolt but managed to replace it easily enough.

Bought replacements for all those bolts but was unofficially advised by the folks at the Nissan dealership to check for air leaks and if there were none, not to worry. So far there are none. I have also recently checked for vacuum leaks using a propane torch and exhaust manifold leaks using soapy water in a spray bottle.

Being in a rush.... I failed to properly attach the electric connection to the ignition coil for cylinder #5. That threw some codes.... and ran rough too. It was an easy fix after I returned from the steelhead trip.

Going forward, I plan on buying a more expensive digital torque wrench for the jobs that can be measured in in-lbs as opposed to ft-lbs. After some reading, I have a much better idea of the limitations of torque wrenches at the extreme end of the advertised working range.
 
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