Ok, just did a major checkover for maintenance and so forth on my '06 TJ sport.

I am at 53,000 KM on a 4.0L

What I found...

Rear diff oil - gross. Changed out for synthetic

Exhaust loose at collector flanges on manifold, both pipes

Rear drum brakes - way out of adjustment ~ self adjusting yes, but they never do

Spark Plugs - Factory NGK regular plugs worn to the point that they were DOUBLE the recommended gap. Gap is supposed to be .035" and they were running .065" with considerable wear.

I was plagued by an off idle stumble and didn't know what to make of it. I assumed an '06 would have platinum plugs, my '02 chevy venture had factory double platinums, I thought all new stuff had platinum. So now the stumble is cleaned up and it seems to pull a little harder. So anyone reading this, check your plugs! I'm hoping for better fuel economy and better torque out of this deal. AND it seemed to rev really rough with a vibration that seems to be gone now; it seemed to kick in around 3500RPM and up, but I didn't notice it today. I'm not a big fan of revving my 4.0L, but occasionally when passing or something I end up above 3500rpm.

She goes good now!

I am an auto Journeyman and really fussy with my stuff, I never imagined that the plugs would be worn to double the gap in 53,000Km. I thought 60 would be a good place to check them.

I thought I would just share this with anyone who was interested so they can get the most from their 4.0L.

Jet

 

So did you put Platinums in?

 

No, I went to Lordco and they didn't stock anything other than the stock NGK number. I'll try to go Iridium next time, but I'll have to research and order in advance.

As a tech I have not been real pleased with Bosch and I won't touch Autolite with a 10' pole. I will hold out for an NGK offering if I can find one next time.

The weird thing is, the 4.0L has a really extended reach and I don't think it is a common plug, there may be no offering in Iridium... Don't know.


I'll look into it in 20,000K

Jet

 

How big of a job did you find it to change the plugs? Special tooling? Remove a bunch of stuff to get to the plugs? Just wondering.... i'm about to get into it.
Thanks,

 

I did my plugs last summer and went to the dealer for them cheapest place I found I put in NGK, was champion in there b/4. Not a big job, providing you don't find one stuck..then take it very easy cause its no picnic if you break one and have to drill it out. When putting in the new ones use the crap they give u so they won't seize in place.
Jet: yu have a 6 speed on the 06 tj? What gear and speed you doing at 3500 rmp??

 

My jeep has the coil packs in a big bar over the plugs. The plugs are easy to change with a really basic socket set. If you have plug wires you just have to be gentle so you don't rip them apart when pulling them off the plug.

One thing I like to do is to use compressed air to blast around the plugs after they are cracked loose to knock the dirt out so it doesn't fall in the cylinder. Not a requirement, but I am fussy.


Yeah, I am an NGK fan too, pretty much all I use.

I have the 6 speed. I try not to spin the engine that fast, I hate spinning inline 6's, I drive my jeep like a big truck most of the time: keep the revs low, use the low end torque, it has lots.. I'll have to go for a burn and see speed to revs though. Usually I am watching the road when I am gunning it! lol

I've never had the jeep over 140K, the thing is really slow with the 3.73's.

 

Hey Dubyacee, noticed you are in loops, maybe I'll run into you sometime...

Jet

 

had to pull ac compressor on my 97 tj i removed the plug no problem but getting new plug started without cross threading was tough so i loosened the belt removed 4 bolts and moved ac compressor a couple of inches only took an extra 5 minutes saved a lot of hassle

 

To get the plug behind the compressor I use a 3" extension,universal joint,spark plug socket and a screw driver to guide it onto the spark plug.

 

I just changed out the spark plugs last night. 30 minute job. quick & easy access with 1/2" socket and a 5/8" spark plug socket, and a 3" extention.. I've owned this jeep since 120,000km, it now has 133,000 on it from when i bought in October. The old plugs had about .060" to .065" gap on them. WORN OUT! Put in the new NGK's and the power is better already. Very happy about it.