Sparkplug change on distributor less Jeep 4.0 I6::

Tools needed:

-13mm socket

-Sparkplug socket

-3/8" ratchet

-3/8" u-joint

-3/8" extension

-Torque wrench

-Anti seize

-Dielectric grease


1) Start by letting the engine cool down for 30 min- 1 hour. In this time you can prep the spark plugs and get the tools you need out. Gap the plugs to .035" and put anti seize on the threads.

2) Un clip the heater hoses and the 3 (2 if you don't have cruise control) cables going to the throttle body from their retainer on the valve cover. Its a lot easier to work and move the rail if these are free.

3) Remove the 4 13mm bolts holding the rail in place. Two are slightly being the a/c compressor and the other two are in the area of the transmission dipstick/ heater hose turndown.

4) Once the rail is free pull it up to free the boots from the plugs. Pull the front of the rail upwards and move it above the heater hose.

5) Unplug the plug located on the back of the rail. You first have to slide the red lock bar than press the button and unplug it.

Image of the plug located on the back of the rail:

The plug with the rail partially removed:

A better view of the plug and the red lock bar:

6) Now you can fully remove the coil rail.

7) If you have a compressed air source available it would be a good idea to blow and garbage away from around the plugs before you remove them. You can see some of what has collected on mine in the photo below:

8) Now you can remove the spark plugs using the socket, extension and ratchet. On the last plug I found that the socket, u-joint and ratchet work the best. Inspect the plugs for stripper threads, color, etc.

Not terrible, but needed a change:

Compare the old plug to the new plug, the gap on the old one was .045" compared to the new spec of .035"

If you notice, that V-grove is worn down to noting but a line.

9) Install the new plugs. I find it is best to hand thread them in with the extension and socket first just to prevent cross threading. Torque them to 30 ft. lbs.

10) Put some dielectric grease in the boots on the coil rail.

11) Install the rail the same way you removed it. Pivot the back down and in.

12) Plug the pack in and slide the red lock bar.

13) Position the boots over the plugs. Make sure all the boots are over the plugs, either by looking at them or putting your hand under the rail and feeling.

14) Put anti seize on the 4 bolts that secure the rail to the block and install them. Torque them to 20ft. lbs.


Some people like to reset their computer after they change plugs, but I usually don't. The computer will eventually learn anyhow.


The plugs I removed had about 40k miles on them. They weren't terrible, but definetly in need of a changing.