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Best spark plugs for the XJ ?

B

BIG-G

NAXJA Forum User
Location
Albany, N.Y.
Its time for the tune up, cap/rotor/msd 8.5 wires/blaster 2 coil pack & now the question to you guys is whats the best plugs to run in my 4.0 H.O. motor???

NOTHING CHEAP, i'll spend the extra $$ for some iriduims if they make a good application!!!

Thanks in advance.
 
NGKs are suppose to be pretty good. I run what the factory suggest also. I do know some of the fella's that run the hot ignitions have problems with them. They do boost your mileage and HP a little though.
 
When I bought my 93 in 03, I immediately put in Bosch Plat +2's. It ran pretty well. As an experiment from what is talked about here, I recently changed for the heck of it to Champs bought from the dealer. YES, there is a difference between the ones the dealer gets and the ones you can buy retail.

After putting them in, the idle smoothed out NOTICABLY, and it runs much quieter as well. My mileage improved as well.

From what I hear, dealers and Chrysler use NGK's as well, but on mine they still carried/stocked the Champion's.

The experiment proved to me that the plugs the engineer's spec'd for the XJ are best!
 
My first chioce is NGK....my second choice is NGK....if somebody is "burning up" NGK's....the heat range selection was poor, or the motor has tuning issues...
 
What's the part# for the NGK plug that fits the XJ?. Did any body try Split Fire Spark Plugs? I am using champion but will buy Split Fire next time.
 
I replaced the factory Champs (which were put in at 58k miles) at about the 80k mile mark two and half years ago with Bosch Plat+2s. I noticed an increase in power and better gas mileage. I'm still running the same set with no problems and I have 124k miles on my XJ at the moment.
I'd love to try NKG Iridiums if they'd make a set for our XJ's, though most people on this site have stated that they'd be overkill in an XJ unless you're running NO2 and keep the engine in the higher RPMs (perfect though for rice burners).
 
Well im definately not putting in champions and i did think of NGK but in my mind there more for the rice burners so looks like i may shoot towards bosch trip platnums. Anyone have a recomendation for wires as well?? I am leaning towards MSD but there kinda pricy and im wondering if its worth it but they would match up with the blaster coil pack.
Opinions, advice welcomed.
 
Champions from the DEALERSHIP. Much better quailty than what gets pushed for the NORM a the local parts house. MOPAR performance wires, and brass conectors on the cap and rotor.
 
Just installed a set of 4412 Champion truck plugs this weekend and am so far very happy with them. Idle is much smoother and midrange power is noticeably better (though not astronomically so). Didn't swap out the plug wires because I don't have any :D (it's a 2000, so uses the distributorless ignition).

Bear in mind that these impressions are after 100 or so miles of service, the old plugs looked like they'd been in there for at least 50000 miles (and two of them were completely misgapped), and I still need to do the oxygen sensors, so YMMV.

They also came with the insulators glazed a deep black, which I understands adds 398bhp.
 
So what about accel plugs?? Anyone running them??

As for wires, i've found, MSD, accel, taylor, splitfire, mopar...any preferences to the best of the best???
 
I'm using Bosch Platinums and Taylor wires in my old 90 xj. Mileage improved and power also but the old plugs were gapped very wide.
 
$1.29 Autolites, MSD wires, and an Accel coil work excellent for me. Remember that sparkplugs are only one part of the ignition system. And regardless, the spark will only be as intense as to what the ignition system can deliver. Plugs can't really be compared unless you do a test with various new units on the same motor and under consistent conditions. There's no way to compare how worn out plugs stand up to a fresh set of plugs! Them worn plugs most likely ran good when they were new. I'd get the Autolites or equivelant and focus the cash on a hot coil, MSD box, brass cap n rotor, better wires, etc.. Spark plugs aren't really a measurable power adder unless your running under boost, then there's a few exceptions.:laugh3:

FUNKYTEE5
 
Ok, let me add this in then, i'm getting MSD 8.5 performance wires,(maybe taylors), Blaster 2 or 3 coil pack and down the road will be MSD's offroad ignition box.....

SO, i really want to match up the plugs to the ignition set up and ofcourse whats good for the 4.0 HO. motor.

Im down to 3 choices, bosch triple platnums, splitfire triple platnums,,,OR NGK PLATNUM IRIDIUM HI TEMP PLUGS!!
The NGK plat iridiums will produce the best overall spark & efficiency but only if my entire ignition system is upgraded as i stated above.

Now does anyone agree with that set up for increased overall ignition performance tuneup & efficiency, "OR" does anyone disagree with the iridiums in the 4.0 HO.????
 
first off, spark plugs from the dealer can be purchased at napa, car quest, and a few other places, there is nothing special about them.... they dont get a special line of plugs or anything like that..... next time, get the part number off the box, and take the part number into a good parts store and they will give you the same thing. NGKs are good overall plugs....along with ac delco, and champion...... splitfire and all the multi tip plugs wont do anything additional unless you are running a very strong MSD style box, and a compatable coil..... splitting a weak spark into a bunch of smaller sparks still doesnt make anymore energy
 
In my old and jaded opinion.....multiple electrode plugs are nothing more than marketing bling-bling....I run a 75HP nitrous shot on my 15 to 1 compression 1327 CC Kawi dragbike using standard B9ES NGK's....11K rpm....no problems.
 
When Bosch plugs came out i nabbed a set for my 4x4 suburban, It lost 3mpg to 6. I installed them in my 95 chero cause they didnt have any Champions in stock, yanked them 1 week later also, lost 2-3 mpg. Put Cheapo Champ back in and it runs great again and gets 18 with 31`s and auto. I ran Splitfires onec in a toyota 4x4, was told they only help V8 with mileage etc, it actually ran way better and picked up 1-2 mpg, The motor was spent pretty much but it was a noticable diff. I run NGK`s in all my bikes except my HD. It seems correct heat range is the key even if the Mfg list shows the correct application. I agree all the dual this, gold plated that, bal,bal, is a waste. I personally have hated Champions for 20 years due to a lost race from a bad plug, I never used them again, but that what works good in my Chero.
 
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