Changing the Spark Plugs in the 3.7L

Spike6901 · **Posted:** Wed Jul 13, 2005 1:54 pm

Changing Spark Plugs on the 3.7L

What you need:
(6) Replacement spark plugs (I installed the factory Jeep plugs for about $2.50 each)
3/8” ratchet set with spark plug socket and a long extension
Channel locks or pliers
Fluid receptacle

Time it takes:
1 hour

How to do it:
1. Remove the radiator overflow hose (about 1”) that runs from the top left of the radiator to the overflow receptacle. You will have to snap loose the hose clips that are attached to on top of a couple of the coils.

2. Remove the coolant overflow reservoir. Remove the top two nuts first, and then the tube that runs out of its bottom by loosening the hose clamps with your pliers. Plug the hole in the bottom of the reservoir, with your finger, remove it and drain it into your fluid receptacle.

3. With a 10mm socket, remove the retaining nuts that hold down each one of the six coils.

4. Unplug the quick connect electrical connection from each one of the coils.

5. Remove the coils by gently working them loose from the plugs which are located deep within the engine. I like to arrange them somewhere to ensure that I get the same one back in the same spot later, but I doubt that it matters.

6. Put the long extension on your ratchet and the spark plug socket and remove the old plugs CAEFULLY! You defiantly do not want to bung up the threads here. The factory installs them way too tight so just be careful. My plugs had 30k on them and they were completely worn out.

7. Install the new plugs buy threading them in with your fingers not the ratchet on the extension. Once you have made absolutely certain that they have threaded in correctly finger tight, then snap the ratchet on and snug them down. Don’t over-tighten!

8. Install the coils with the retaining nuts, plug them in, and install the coolant reservoir and hoses.

That’s it! Congratulations on saving yourself some cash over having it done at the dealership.

DoverKJ · **Posted:** Wed Jul 13, 2005 2:05 pm

That is a good post. Very helpful

Thanks

I always like to replace plugs, and wires if required, one at a time so that I do not get them mixed up.

JJsTJ · **Posted:** Wed Jul 13, 2005 3:58 pm

No plug wires on the KJ, individual coil packs, 1 per plug. The way the wire harness is routed, it would probably be difficult to mix them up.

I have done my plugs twice in 31k, once at 15k and just this past weekend at 31k and both times the plugs were pretty well worn.
The OEM NGK plugs were about $2 ea. at a local parts house. You do not have to get them at the dealer, nothing special about them either, just good ol tried and true NGK V grooves.

On my 2003, I have been able to get away w/ just unbolting the overflow bottle and moving it up onto the top of air box, holding it in place w/ a bungee. No disconnecting any hoses. Might be different on the 04?
Whole job took about 45 mins to finish.

Good write up, I did my plugs this past weekend and thought about a write up just never got around to doing one.

Would you like it moved to tech?

DoverKJ · **Posted:** Wed Jul 13, 2005 4:03 pm

Sorry for the mix up, I was referring to when I previous changes the plugs in my XJ and other vehicles I previously owned. I know that the KJ has the coil packs, it has always just been easier to do one at a time so that nothing gets mixed up.

Sorry for the confusion.

Again, good write up.

Brian

Spike6901 · **Posted:** Wed Jul 13, 2005 4:07 pm

It is up to you if you would like to move it to Tech. I just thought it may help out some newb's if they need it. I suppose it may be helpful to move it there.

JJsTJ · **Posted:** Wed Jul 13, 2005 4:39 pm

Spike6901 wrote:

It is up to you if you would like to move it to Tech. I just thought it may help out some newb's if they need it. I suppose it may be helpful to move it there.

No problem on moving it. The Suggestions forum is more for forum suggestions and such. THis is a good thread that may help people here in tech.

To some changing plugs may be a simple process that they are very familiar with on many different types of vehicles. However, I know there are many new people that have never worked on a vehicle before and this might help them out. THis is exactly what this forum is for, To help as many people as possible w/ all aspects of taking care of or modding their Libertys.

John

JJsTJ · **Posted:** Wed Jul 13, 2005 4:43 pm

DoverKJ wrote:

Sorry for the mix up, I was referring to when I previous changes the plugs in my XJ and other vehicles I previously owned. I know that the KJ has the coil packs, it has always just been easier to do one at a time so that nothing gets mixed up.

Sorry for the confusion.

Again, good write up.

Brian

Brian, No confusion here, no mix up. I was just clarifying about the KJ's setup. Actually, your statement is a good suggestion. Doing one at a time regardless of the plug wires is a good idea. On vehicles w/ plug wires, I do the same thing. I learned the hard way, by mixing wires up and having a vehicle that ran like crap after doing a tune up. Thanks for your input on the subject, I am sure it will help someone. :wink:

DoverKJ · **Posted:** Wed Jul 13, 2005 4:52 pm

No problem. I have about 25K on the KJ as of now. I am getting ready to change the plug probably during the next oil change. The write up of the change will be helpful as I did not knwo that the overflow tank was in the way. I will probably do as you did and just lay the tank on top of the intake so I do not have to drain any coolant or disconnect the hoses.

Brian

Eddo · **Joined:** Thu Jul 07, 2005 7:01 pm **Posts:** 1214

I was able change the plugs without touching the overflow bottole. Not sure if mine is different but all I had to do was stand on the bump and just reach in from the top.

I changed mine at 28k and they where plenty worn. Maybe next time I will not wait as long.

Spike6901 · **Posted:** Wed Jul 20, 2005 12:47 pm

Yeah, it can definatly be done. I just found it easier to yank it out so that I didn't have to fight it and reach arount it

. It is only a couple of nuts and a clamp.

Joe Jeeper · **Posted:** Sun Sep 25, 2005 10:17 pm

I had to kneel on top of the radiator to change mine, I didn't want to mess with the coolant overflow tank. I put them in at 30K the old ones were worn I'm trying Bosch Platinums, seems to be running stronger! Joe

ARBSeth · **Posted:** Tue Oct 25, 2005 6:54 pm

This might be a dumb question...

What's the gap on the plugs?

djformi · **Posted:** Thu Dec 08, 2005 9:20 pm

0.044

ARBSeth wrote:

This might be a dumb question...

What's the gap on the plugs?

SavageSS27 · **Posted:** Sat Dec 24, 2005 12:40 am

OK, just a little add-on for the retards (me). MAKE SURE THE ENGINE IS COOL BEFORE DISCONNECTING THE COOLANT HOSES!!! I just found this out the hard way, and will need to spend some extra cash to have the engine compartment cleaned.

QuietOutdoorsman · **Posted:** Fri Dec 30, 2005 3:24 pm

What does the Jeep shop manual specify for torque on the spark plugs? Every other vehicle I've ever had has that on a sticker in the engine compartment.....plug gap (for stock plugs) and torque....but not the KJ. It just has the plug gap and it's wrong (say 0.040" when NGK says 0.044").

MikeD0106 · **Posted:** Sun Jan 08, 2006 4:39 pm

Well, I just changed mine out yesterday. It was my first mechanical challenge performed on the KJ. So far... Everything works. *Always a plus*

As far as the torque. I don't know of any specific number so I just tightened mine down a little past hand tight. It's not as tight as factory, but shouldn't be a PITA the next time I change them.

krazz1e · **Posted:** Mon Jan 30, 2006 2:06 pm

on the engine bay it says 0.40 on gap. When i took the stock plugs out they measured 0.42. I gapped mine at 0.40 and installed. They are working great. by the way I used a Champion plug because they were out of the NGK.

mine were shot at 30k.

jsstover · **Posted:** Tue Mar 28, 2006 12:30 pm

Has anyone ever used a little bit of that silver anti-seize on their plugs. I used that on my old chevelle all the time and was glad I did.

JeeperCreeper · **Posted:** Sat May 27, 2006 9:04 pm

I changed mine out the other day. 101k miles and it still had the original plugs. Aparently the person who owned it before me didn't do any regular mantenance. When I first bought my libby the oil change sticker on the windsheild was from 19k miles ago!.. Anyways I'm getting way better MPG now with the new plugs. I went with Bosch Platinums. Runs alot smoother now too.

AdamIsAdam · **Posted:** Wed Jun 07, 2006 11:50 am

I love this board!

I was wondering what's special about doing this job on the KJ. A quick looksie into the Tech Section, and there it all is.

I'm hoping to get around (pun intended) that coolant bottle.

i've noticed that the KJ has been taking a little longer to start up lately and I'm thinking it's the plugs. I'll check, but I think I've got 20k on them now (52k on the KJ).

Changing the Spark Plugs in the 3.7L

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