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NGK Iridium IX Plugs Rock!!!

Sorry dude, but the stock Champions are hard to beat. Have experienced mega problems with a variety of 'specialty' plugs in the past in many vehicles. Is always safest to stick with what the vehicle was delivered with.
No flame intended, but I too am skeptical (and without a dyno handy to affirm or debase)

But FWIW running Bosch Platinum (not the 4) with .035 gap, Bosch wires, Autozone cap/rotor, cat, $25.00 muffler (tore the last one off) and not displeased...but how to quantify any improvement?

It starts, it stays running, gets 15-18 MPG - depending on my foot I suppose- just a stock '89 4.0 with 192k and aftermarket tune-up stuff/air tube & KN cone on 87 octane...no knocks (no knock sensor LOL) or other hassles. won't win any cool points with it but ... it runs.

How is it that these plugs are better?


What improvements did you notice? I have friends who run them in Hondas, and they swear they noticed an improvement. Im a little skeptical though. How much did you pay for them?
i am interested in those plugs too. but what makes them awsome? what does that mean? what makes them awsome?
you got to give more info. jack
Holy crap, have you seen his website? That aint no mall cruiser! I think he has a little experience credibility just by virtue of what he has done to his XJ.His mod list looks like a friggin parts catalog!
yeah, i gotta agree with Lucas...

when he says he's tried every other plug...im gonna hafta believe him...it looks likes he's tried/currently running almost every aftermarket XJ mod u can find!

i WOULD like to know SPECIFICALLY what he thinks makes those NGK Iridium IX so good though....
(after being a champion guy and getting talked into blowin $ on the bosch platinum +4's and not really noticing anything great with em)

That's what I was asking...

how do ya quantify "great" spark plugs??

MPG gain over a few tankfulls to prove it wasn;t just a holiday tankful?
1/4 mile time slips with ___sec off the old ones?
Dyno run with #s?

I dunno but I just went from 3.55 open to 4.56 with a spool. I "seem" to be getting better MPG but need 2-3 tankfulls to confirm that, also seem to be catching myself speeding alot...need to do a 20 mile -+ run up the interstate to verify the speedo is right, or what calibration factor to apply.

Again to emphasize, not flaming Fred... He IS an enthusiast and not a bullshitter. I'm just wondering how he bases his improvement. Momma's Jeep could use a tune up and if these NGK are ther real deal, I'll buy em.

Guy's as far as the MPG numbers I dont know yet, but I have to say as far as idle & throttle response there is a noticable difference. The first plugs I ever used where Split Fire (gapped to .055 & lower)w/ Jacobs Ignition & the idle was garabage along w/ throttle response. I went w/ the Accell 300+ because of the size & spec's w/ NGK V-Groove also started out w/ gap @ .055) & there was a big improvement compared to the afor mentioned. Then I went to the Bosch Platinum +4 (cant gap) & I was a little scepitacal (spelling stinks) but it wasn't bad. I left them in for a couple months then checked them & I was getting some white deposits on the electrodes. I checked out NGK's site & I saw these new plugs (Iriduim IX), heard good thing's w/ imports & others that used them but I noticed they didn't list them for my year XJ or any XJ for that matter. I e-mailed NGK & the tech said I could use them w/ the part# he gave me. So I ordered them from Mornarch (http://www.monarchproductsinc.com/ngk.htm) for $6.99, gapped them to .050 & noticed an instant improvement @ idle & throttle response compared to what I've used. Guy's I wouldn't steer you wrong. If you are running an aftermarket ignition I would try these. I'll post the part # NGK gave me for my '97. Fred
damn, thats a lot of change for a plug. Whats the life expectancy of these things? Im pretty happy with a good cap and performance wires, nothing fancy. You think they will do anything for stock ignitions?
and can you gap them yourself or will you damage the electrode?
Holy crap Fred, you must have THE most expensive XJ around...man I remember when you first got that thing and were just getting started with the mods....Youve comea loooooong way, good job! All you need now is a PUV rollcage and you're set :D Going to Moab with that beast?

By they way I have read good things about the Iridium plugs too, right now I am using Bosch +4, originally I only used to use NGK V-plugs, with great results by both. The engine shop that built the Warrior's engine dynoed all the popular hi-po plugs on a Chevy race boat engine and NGKs produced the most power; Splitfires actually were less than baseline! I only went with the Bosch this time due to longer life a plat. plug provides for, but supposedfly these Iridium will last even longer, so my next set will probably be those too.

Makes me nervous-

You guys talking about widening the plug gap so extensively makes me nervous!! My years of auto experience has shown me plug gap is really very critical to proper operation of the ignition system. By doing that you are subjecting the entire system to way more loading due to the increased resistance. Or are you saing these plugs are so miraculous they automatically increase voltage and lower resistance as to allow this increase?? How can this be possible??

Keep this in mind- by saying you have increased mpg and perfermance using these plugs your engine was misfiring before, or at least not experiencing complete combustion. In later XJ's the ignition systems are really quite good in purely stock form- they had to be to conform to strict emissions standards and dang sensitive OBD II restrictions.

Their reported performance improvements in Hondas and the such i'd bet may be felt at higher revs, where ignition requirements are particularly critical. High rev performance standards are certanly of no value with the 4.0.

That price gives me the shakes too-
I have to agree about the stock Champions. I used bosch platinum on the 2000 Moab event and had engine trouble on one of the runs due to fouling. Back at camp, I bought a set of split fires from Charles, they ran very good for the remaining event days, but by the time I got home they started fouling. I replaced them with stock Champions and didn't have to change them for 3 oil changes. It is a daily driver so it get a good deal of miles on it. Just wanted to add my 0.02 cents,