I figured since there wasn't a DIY for spark plug changes, I'd write one. It's not difficult at all, so nobody should have trouble.


level of difficulty:
1.25 out of 5 (5 being hardest)


approximate install time:
less than 45 min (longer if take optional steps)


tools:
ratchet with a long extension
10mm socket
5/8" or 16mm spark plug socket
torque wrench (both inches and feet would help)



Spark Plugs:

*Optional: If you do want to spend a little more time removing the plenum/intake duct to make the job easier, follow the directions as outlined in the Motordyne's installation guide.
http://motordyneengineering.com/manual.pdf

If you don't mind all the crap that's in the way of the spark plugs, then read on from here.

1.) First locate the coil packs. These will have a harness attached to them. Unhooking these harnesses make the job easier. Use the 10mm sockets to unbolt the bolt on the coilpacks. It helps if you have a long extension. Some of the coilpacks are hard to get to, as there are things in the way. These bracket-like things (gold in color) can also be removed with the same 10mm socket, if need be.

Here's an example of what the coilpack looks like.


Here's a picture where you can see the harness (gray plastic pieces the coilpack is hooked to).


2.) Remove the coil packs - you can just pull them out once the bolt is off.
[no pic]

3.) Insert the spark plug socket (5/8" or 16mm) with a quick release long extension in the hole the coilpack was in. It should be removed with little effort.



4.) Install the new spark plug and torque it down to 15-21 ft-lb (180-252 in-lb).
[no pic]

5.) Install the coil pack and torque the bolts down to 64-95 in-lb (5.33-7.2 ft-lb).
[no pic]

*If you removed the plenum and the intake duct, then follow the directions as outlined in the Motordyne's guide for re-installation.

 

What about orienting the spark plug so that it fires towards the exhaust valve is it? What is that procedure called? Adding shims of varying thickness to get it torqued down all facing a certain orientation...

Anyway, my question is where does one get the spark plug shims of varying thickness and how does one orient the spark plug (i.e. which way should it face)?

 

I think the process is called indexing. BTW, I really don't see a point in that. I'd assume a very very small difference, if at all, from all that work. If you still want to go ahead, then I suggest you look up "spark plug index" or something similar.

 

What spark plugs do you recommend on a 03 fully stock and what gap?

Thanks

 

For stock, use PLFR5A - 11. They come pre-gapped, so no need to touch them.

 

What about a moderatly modded NA car? I could use OEM plugs I'm sure but any performance gains to be had with other plugs? (Mods listed below). Thanks,
Fletch

 

The differences between different spark plugs are negligible, but I guess theoretically a hotter spark plug would yield that positive difference.

 

Hotter plugs need to be used if the plugs can not maintain enough heat to burn off residue, as this will cause fouling.

Colder plugs are used if the plugs are not cooling down enough between each burn cycle, this will cause pre-ignition.

Plugs are a balancing act, it is best to stick with the recommendations of the manufacturer and use oem or aftermarket plugs specified for that application unless your car is heavily modded, in which case search these boards and talk to experts about your setup. Otherwise you are more likely to do harm than good.

Chris

 

I did some research on "indexing" when it came up before. It is not proven that there are any gains to indexing spark plugs, meaning, there is no dyno proof that I was able to find. Secondly, most of the newer plugs are "self indexing" with multiple grounding straps (most higher quality plugs that is, ie platinum etc.) The article I read, the guy did index his plugs, and in order to do so, he had to buy several sets, mark where the grounding strap was on a visible part of the plug, then put the plug in the motor. Only then could he tell if it was properly indexed. If it wasnt, he would pull it out, and try another. Sounds pretty spendy if you ask me, and for a minimal gain, if any.

good write up.

 

They used to sell indexing shims, so you could shim the plug a little this way and a little that way to get them straight. The thing about it is, back in the day (or if you have a car that still uses back in the day technology) you only had one valve. Most of the time, the valve would be on one side of the head and the plug stuck in some odd angle of the other, so indexing has its roots in some sound reasoning. You did not want your spark firing into a shrouded cylinder wall, especially considering your ignition systems ran on good old fashioned points and condensers systems.

These days the plugs are in the middle of the cylinder and with half of the roof taken by intake valves, the mixture will completely envelop the plug. This is one way cars today develop so much emissions restricted power per liter compared to the cars of yesterday.

Chris

 

If I remember correctly, I read somewhere that platinum plugs are not recommended, as the platinum plug can fall off into the cylinder. I read that quite some time ago when I bought new spark plugs.

As for spark plug types and gains... I doubt there's hardly any if at all. Just for my own reasons, I had to buy the NGK Iridium plugs. :-\

 

Nice short write up. It looks like a PITA to do but it's key to just moving the intake, strut bar, wiring, etc (which is not that difficult) out of the way to remove the coils. The job is also a bit easier if the coils are unpluged and removed while removing and replacing the plugs.

 

this may be a dumb question...

yes the HR engine is different, anyone do plugs on a HR yet? *doubtful*
would i be looking at the same places for the plugs? could i expect the same level of difficulty?

i got another 20k to go before i really have to worry about it though
if it's as easy as this... i cant wait! lol

doing the plugs on my 4th gen fbody..... oh man.... i dont want to go there again

 

Ok.. Nice DIY which led me to save $225 labor at the stealership.. But no fukin way u did this in 45 min... U must be one fast ****.. It took me 2hrs..

 

This DIY should be almost/if not exactly the same as a DIY for changing plugs on a VQ35HR motor.

 

Hey guys,

quick question...

Last night I replaced my spark plugs and also installed a 5/16 iso spacer. I am trying to figure out where my problem might be. It was getting late and there is a possiblity I missed something but until I look at it today I just want some options

After I finished with the plugs and install I start the car and the revs up and then bogged down and stalled the first time. Ok learning curve then I start it again and it idles rough for a little bit and then bogs and stalles again. Really violent shake bog. So then I try the reseting TB and Idle air per the instructions.. Still no good.

I am posting here to see if there is anything the plugs and coilpacks can do to make this happen. I am talking with Tony now also.

I have the coilpacks in the right order: Left side 1,3,5 and right side 2,4,6. I first check this. I bought the pregapped plugs so no gapping was checked. They are all the right plugs.

One other thing is my buddy was taking the coolant hose off the Tb and some leaked out and possibly got onto a sensor on the back of the engine. The green clip in the back. I dried it off. But would that cause anything?

It could be a massive air leak I just don't know until I take it apart again and recheck everything(today)

Thanks a lot for the replys guys

Chris

I didn't want to start another thread up. But mods if you want me to I will

 

make sure you payed attention to the little rubber near the oil filler cap. if you dont pay attention and move it out of the way itll go between the spacer and the plennum and make a huge leak. thats what happened to me the first time i did it. symptoms sound fairly familiar. do a smoke test. should tell you where its leaking. most likely air leaking somewhere.

 

Hey guys thanks for the replies. I found the problem. I didn't pay attention to where the fuel pressure regulator was mounted(on the bottom of the bottom plenum.) I thought it fit between the Bot. plenum and the top with the spacer installed. It looked werid and didn't fit right. SO almost taking the car apart I decide to take it out between and guess what a hughe air leak. Those bolts weren't even tight

SO thanks for the help and the great thread on Spark plugs Helps a bunch

Chris

 

Every how many miles do I need to change spark plugs? I got 27k miles on my Z and never changed them. My car has a rough iddle and when I turn on the ac the revs go up a lil and get rougher, kinda unstable rev in neutral. WHAT CAN THE PROBLEM BE?

 

any mods on your car?