Today I thought I'd inspect my spark plugs since they've never been inspected after 4 1/2 years of use and about 46K miles. I was also wanting to loosen the plugs because it's always a good idea to reseat plugs in aluminum heads to reduce the potential for seizing and cross-threading because of steel composition of spark plugs.

I'm a mechanically inclined guy and I had never really paid much attention to the spark plug access on this VQ motor. My 96 Maxima's plugs could be changed in about 20 minutes, but on the G VQ35, there are all kinds of wiring harnesses and vacuum lines in the way. Access to the plugs on thsi car brings back bad memories of changing plugs on my LT1 Z28. For the G, I had to remove about 7 10mm bolts to free up enough access and tension in the wiring harness that runs above the passenger side cylinder head. Since I didn't want to waste my entire day, I decided I'd only do cylinder #1 (front passenger side). Wow, that took nearly 20 minutes just to access the coil pack and plug and it was tight. The plugs was in there tight, but nothing too significant. The plug was burning clean and the gap was at spec so I threw some anitseize on the threads and reinstalled the plug, coil pack, and numerous bolts.

I had never heard anyone mention how hard it would be to replace the plugs on this car. It doesn't look hard, but it would easily take an average mechanic about 2 hours to do the job. I'll hold off for another 25K miles then replace the plugs.

 

Dude, I'm not mechanically inclined at all. It took me four hours to swap my stock cats to the kinetix a little over a year ago. It took me a little over an hour to simply rotate my tires front to back just last week. The day before, it took me about 2 hours to take off and put back on the plenum.

I say all that because IMO changing the plugs last year was one of the easiest things I've done yet to this car. It only took me an hour to change all 6. Granted - it wasn't *easy*, and it could be better, but I highly doubt a mechanic is going to spend 6 hours swapping plugs.

 

I didn't say it would take 6 hours. I figure 2 hours is the typical shop time. It would probably take me longer because I get pretty nervous about moving around wiring harnesses because the last thing I want to do stress one of 50 wires in the main harness. The driver's side looked easier after the intake pipe comes out, but I didn't study it too much. I was just surprised at how Nissan crammed so much equipment acroos the top of the coil packs and plug cylinders.

 

Crap. I mistyped; I didn't mean 6 hours, I meant 2.

But yeah, there's a lot of crap in there. I was surprised myself when I was installing my strut bar. Things that I never noticed before.

 

Uh oh... I have new irdium plugs coming, I guess I would now hold off until the weather gets warmer....

 

Anyone have a good DIY spark plug change link with pictures? I want to change mine out soon but sounds like they are hard to access.

 

I pulled off my plenum and took off the lower intake manifold, it was easy accessing everything then!

Someone once told me that you could swap out all 6 plugs with removing any 'major' parts but, if I were to do it again, those parts come off so easily that it's worth it just for the space to work.

 

the previous time I changed plugs, it took me 56 minutes and that included re gapping each plug down to .035.

just last week, I changed to the copper NGKs but I had the upper and middle intake manifold off, and it took about 10 minutes....if that!

somewhere I did a write up on changing plugs............

 

here it is:


we really need a DIY post for this topic.

I just changed my plugs to NGK Iridiums. Here's the procedure and tool list.

TOOLS:

6 NGK LFR6AIX-11 Iridium IX Sparkplugs (these are 1 heat range cooler than stock)
3/8" Rachet
3/8" long extension (at least ten inches)
10mm socket
16mm "deep" socket (or "sparkplug socket")
Magnetic pick up tool
3-prong grabber (optional, you'll need it if you don't have a "sparkplug socket")
Pliers
Torque Wrench

Most people would have these tools in their garage. The long extension is a must. The magnetic and pronged "pickup tools" make this much easier.


PROCEDURE:

1) DISCONNECT THE NEGATIVE BATTERY TERMINAL!
2) Remove the engine cover. it is 2 10mm nuts and 2 10mm bolts
3) Remove the intake tube. This should require the removal of (1) 10mm bolt and 2 hose clamps. Don't forget to disconnect the rubber breather tube; use pliers to loosen the clamp. Tne pull the rubber tube away from the intake pipe.
4) Let's start on the driver's side first.
5) There are 3 coils on each head. They are held in place with a single 10mm bolt. Underneath these coils are the sparkplugs.
6) to gain better access to the coils, you'll need to remove 3 10mm bolts which hold down an electrical harness just above the coils. All the bolts are easy to get to. You may have to push a couple hoses out of the way to get the back bolt though. Be care ful not to drop the bolts!!! The magnetic pick-up tool can be very helpful here!
7) After you have removed the bolts for the electrical harness, Disconnect the plugs going to the indiviual coils. There are 3 plugs to undo. They are snig, but they come off fairly easily with just your fingers. Remember which plug goes to which coil. That is extremely important!!!!
8) Now you have good access to the coils! Use the 10mm socket to remove the bolt from the coil. Once you have removed the bolt, the coil will pull straight up out of the head. This should be very easy to pullout.
9) You should be able to see the sparkplug in the hole. It is pretty far down there.
10) Use the 16mm socket with the extension to remove the plug. If you aren't using a sparkplug socket, you'll need to use a 3-prong, spring loaded pick-up tool. This tool makes plucking the plug out the head very easy. I'm sure you can come up with some other sort of tool to do the job, but that is what I used.
11) Replace the sparkplug with your new plug! Torque the plug to 20 FT-LBs! Make sure not to crossthread or overtorque the plugs! Aluminum heads are easy to strip out!
12) relplace the coil; torque its bolt to 95 IN-LBs and plug it back in to the harness.
13) Repeat steps 8-11 for the other 2 cylinders!
14) Now, you have completed the driver's side of the engine. Don't forget to bolt the wiring harness back into position with its 3 10mm bolts.
15) You can also replace the intake tube at this time.
16) On to the passenger's side of the engine.
17) This side is slightly harder....only because some of the bolts are difficult to reach by hand.
18) I started by removing 2 10mm bolts which retain the wiring harness. I only removed the 2 bolts closest to the front and middle of the head. The rear bolt is not necessary to remove.
19) You will need to remove the rubber breather tune that runs from the valve cover to the intake manifold. Use the pliers to loosen the clamps; then, slide the tube off of the engine.
20) Now, you should be able to disconnect the electrical plugs from the coils. This is the same as on the driver's side.
21) The coil removal and plugs change is the same as described above. The only difference is that the back (toward firewall) coil bolt is difficult to get to with your fingers. Use the magnetic tool to remove and replace this bolt.
22) After repeating the procedure for all the cylinders, you should be done. Make sure to check that all the electrical connectors are snug and "clicked" tight.
23) Very important, you shouldn't have any extra bolts laying around!!!!
24) put the engine cover back on. Secure it with its 4 fasteners
25) reconnect the negative battery terminal.
26) YOU ARE DONE!!!!!

I think I remembered all the steps. This took me about an hour, going at a leisurely pace. Additionally, I was figuring it out as I went. With some motivation, you could probably do it in 1/2 an hour.

Have fun,

Andrew

 

Thanks for the info QuadCam.

 

We just replaced mine with the help of a Nissan mechanic buddy.....

It took him maybe 20 min. He was used to it.

 

the last 2 are the pain...i changed mine out at 40k or so...

 

\no problem.......it's alot easier when someone else has done it and explains it.

Also, I just updated it with torque specs for the plugs and the coil pack bolt.

 

no lie... it took me 45 mins reading the instuctions posted on this forum

 

I've read the directions and my 03 must be different because the wiring harness on the passenger side goes directly over the coil packs and even after removing the bolts (removed way more that 2) securing the harness, the harness is still very tight and hard to move. It's location totally impedes access of socket and extensions into the head unless you physically push the harness out of the way which I reluctantly had to do. I also had to unclip a harness from the coolant hardpipe near cylinder #1. If I didn't unclipped this harness, I would have stressed the harness way to much during removal of the coil pack and plug removal/installation.

You should be really careful when doing this job, especially if the plugs have never been removed because if don't have the socket fully seated and you're not applying torque directly to the top, you run a very real risk of cross threading the plug and that can be very expensive.