Getting back to
basics. We all
enjoy trying to come up with a decent write-up on lift kit installs or
bumper installations, but you still end up back at the basics when it
comes to the engine. Sometimes even the basics can be overwhelming to
the novice tuner. With the current growth of offroading and the influx
of new Jeepers, both guys and gals, and with Jeeps coming out of the
factory plenty capable as they are.....well let's just say that there
are a lot of inexperienced novice Jeepers out there. So this is for
them, and if any of you more experienced folks out there get something
from this, even better.
Changing spark plugs
hard. Right? No, not really, especially when your rig is newer. Many
years ago, I learned this procedure with plug swaps. There will be a
extra steps taken that in the long run can make that plug change
30,000 miles from now go smoothly. This installation pertains to the
4.0 I-6 engine.
supplies for installation
are easier to use than
- Socket wrench
- 6" extension
- 13mm socket
- 5/8" Spark plug socket
- Feeler gauge
- Dielectric grease
- paper towels or rags
- I use but didn't show a pic......flex knuckle
There are a lot of
of spark plugs out there. Many different flavors and prices. I won't
any particular brands. I will say that it's been my experience that the
expensive gimmicky ones are just that, expensive and gimmicky, but I
haven't seen any true gains from them. Also avoid cheap import "X"
brands. They're not consistent at all. For my swap, I chose Champion
Truck Plugs #4412.
Installing new plugs
without checking and
correcting the gap is just a waste of time, effort and money. Gap is
important for consistency for the fuel burn in the cylinders. Running
too narrow of a gap and the flame
will get squashed and doesn't give a good burn. Too wide
of a gap
miss fires. The spark may decide to start jumping to the cylinder wall
or piston dome, either of which causes hot spots. Hot spots inside the
cylinder burn off the incoming fuel charge before the plug fires.
The recommended gap for the TJ is .035 or 35
thousands of an inch.
You want the gauge to slide between the electrode and
ground with a
little resistance. If it's too wide, tap the end gently to close. Too
just pry up on the ground to open. Gap all 6 and set them aside. If you
drop any, check the gap again and make sure the ceramic didn't break.
I like to lay
the hood back against the roof. If it's windy, bungee it
in place so that it can't close on you. You can use the prop, but I
that it makes getting to the rear plugs difficult.
If you have an
earlier model built prior to 2001, you
will notice a couple
major changes have been made. Gone are the distributor and plug wires
that were replaced by a distributorless ignition and spark plug power
rail. There are many bonuses to this new set up. All it used to take
was water on the wires or a hairline crack in the distributor cover to
leave you stranded. No more having to pay attention to what wire came
from what spot on the cap.
At this point if you
do have a model with plug wires,
only changing one plug at a time so that the wire order doesn't get
you have the power
rail, it will need to come off so that you can
get to the spark plugs. There are 2 bolts at the front and 2 at the
rear. Use the 13mm socket wrench to remove these.
Watch out for the red
the alternator hiding just under the
socket wrench. Hit that by accident and you could weld the wrench to
There is a bolt just
tube from the airbox to the throttle
body. You can either remove the tube or use a wrench or swivel to
remove that bolt. After removing the 4 bolts, grab the power rail
from both ends and wiggle and pull until it comes loose. It can fight
a bit until the suction of the boots lets go of the plugs. It's wired
into a harness and wont go anywhere so just let it sit out of the way.
the 5/8" spark
plug wrench and remove the old plugs. There is a
difference between a spark plug socket and a deepwell socket. Spark
sockets are tapered inside to help support the plug and a rubber
grommet to help center and hold the plug from dropping out when you
turn the socket with the plug end down. Its amazing how easy you can
break the ceramic with a standard 5/8" deepwell socket.
important extra couple of steps
I learned many years ago that using
products properly can make servicing vehicles a pleasure instead of a
just like says.
It keeps threads from seizing or freezing so that the bolts can be
removed more easily in the future. I put a very small dab on the spark
before threading them in.
Take some care and hand thread
the plugs in. Don't cross thread the
plugs. Cross threading is easy to do when you're working in tight
spaces at odd angles. So thread them in till they stop. There are 2
different methods on seating plugs. This depends on how they're made.
Some use a washer or gasket. You only tighten these a 1/2 turn with a
socket wrench from the point where they're hand seated into the head.
other type has only a bevel and this type requires only 1/16 of a turn
past hand tight with a wrench.
important step is by putting a small amount of Dielectric Grease
or tune up grease into the spark plug boots. Dielectric grease is great
stuff. It's made specifically for electrical connections that are
subjected to extreme conditions or elements. It will keep out moisture
and promotes conductivity. It also keeps the boots from cooking
themselves on. This will be important in 30,000 miles when your trying
to install new plugs again. It makes the boots come off nicely without
Push the rail back onto the spark plugs. Then put a
dab of anti-seize on
the rail bolts and thread them back in. Hand tighten and torque to 20
Well that's about it, you're done with this. I can't stress enough the
importance of using the Anti-Seize and Dielectric Grease. It really
will make that next change go potentially a lot easier. Nothing worse
than having a torn plug boot or have a wire tear out or one of the
plugs frozen in.
can use these instructions however you choose, but I am not liable for
anything you do Please feel free to link to them from other sites, but
you must get my permission first before copying them off of this site