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Old 05-09-2011, 01:51 AM
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Best spark plug for the 4.0?

Anyone have good or bad luck with a particular spark plug in the 4.0 04' model. Just bought my Wrangler and want to tune it up. Thanks in advance.

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Old 05-09-2011, 09:23 AM   #2
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I've always run the factory NGK's. No issues whatsoever.

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Old 05-09-2011, 09:30 AM   #3
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I'll assume from the 04 that you have an 04 TJ. I've been using Autolite APP985s for about 10,000 miles since replacing the OEM plugs with no issues.
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Old 05-09-2011, 09:31 AM   #4
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Thread link on discussion of plugs. Jerry's very knowledgeable when it comes to this.

https://www.wranglerforum.com/f5/new-plugs-87640.html
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Old 05-09-2011, 09:41 AM   #5
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Funny I just finished tuning up the wifey's. I went with Bosch Platinum's.

I pulled I swear the originals out (136000 miles) as the wires/cap/rotor were all mopar.
We just bought it, so it needed it. Plugs were worn down to nearly a 60 thos. gap, center electrode was just barely visible.
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Old 05-09-2011, 09:54 AM   #6
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I replaced the factory plugs with Champion 7034 plugs about 6,000 miles ago. No issues or problems what-so-ever. I really like them.

When putting the coil rail back on, make sure you get the boots completely over the plugs - it sounds elementary, but it's much easier said than done.
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Old 05-09-2011, 10:53 AM   #7
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Champion 7034, Autolite APP985, or factory NGK's will work just fine.

Caution: do NOT buy single platinum plugs. they don't work in distributorless ignition systems used on newer model TJ's.
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Old 05-10-2011, 12:21 AM   #8
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Auto Zone currently has a good rebate on Autolite plugs. I just installed Autolite APP985 in my '01 4.0 Sahara. Cost $4.49/each with $1.50 rebate each. Seems to start quicker and idles smoother than the Bosh platnums I'd had in there the last 30,000 miles. Haven't driven enough to tell much else about them.
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Old 05-10-2011, 03:59 AM   #9
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I have a buddy that currently works for an independent auto shop. He used to work for Chrysler, he still recommends what came in it factory. Says for some reason the 4.0 can be picky...
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Old 05-10-2011, 10:48 AM   #10
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The 2000 and newer 4.0L is indeed very picky about the spark plugs it runs on due to its DIS (distributorless ignition system). It fires on both the compression and exhaust stroke which places additional demands on the spark plugs.

Because the spark plugs fire twice as often with a DIS-equipped 4.0L engine, conventional spark plugs like the NGKs a few keep recommending will only last half as long in the newer DIS engines as they would in an older non-DIS engine. Personally, I would only run dual-tipped platinum like the Autolite APP-985 or Champion 7034 or the new iridium style spark plugs like Autolite's XP-985 in newer DIS engines.
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Old 05-10-2011, 10:58 AM   #11
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I vote Autolite....I have had zero luck with anything champion makes
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Old 05-10-2011, 11:15 AM   #12
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I've always run the factory NGK's. No issues whatsoever.
I agree.

most problems come from aftermarket plugs. Splitfires, cheap replacements, etc... Not to say you can't get a bad NGK out of the box, but I stick with what works. As for the autolites, thats what I use in my fords.
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Old 05-10-2011, 11:18 AM   #13
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Conventional spark plugs like the NGKs will work fine in the newer DIS engines but they will erode their spark plug gap at twice the rate on a newer DIS engine as they would in an older engine. That simply means a conventional spark plug will only last half as long in a DIS-equipped 4.0L engine made 2000 and later than it would in an older engine. That's why I don't recommend any conventional spark plugs in newer 4.0L engines. Dual-tipped platinum or the latest iridium tipped spark plugs will easily exceed 100K miles without spark plug gap growth which means the engine will run well on the same set of dual-tipped platinum or iridium tipped plugs for 100k miles. Conventional plugs will typically only get 15-20K miles before needing to be replaced.
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Old 05-10-2011, 12:39 PM   #14
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I vote Autolite....I have had zero luck with anything champion makes
I almost agree with the above.

Only difference is my '65 Olds Cutlass F-85 doesn't like Autolite at all. Never had any problems with Autolite in any other GM's I've owned in my life.
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Old 05-10-2011, 01:04 PM
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Thanks for all the help, after doing some research I went back with the NGK plugs, my Jeep has 88,000 miles on it and from the looks of the plugs I removed that was the first time they had been changed (had about a .80 gap) It ran good before the change but much better now, silky smooth. Hopefully my mileage will go up a tad!
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Old 05-10-2011, 01:40 PM   #16
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The following is purely the opinion of the user:

Don't put Autolite plugs in your Jeep. Autolite is made by allied signal, who makes Fram and Fram is crap. If you want a real spark plug, use Champion.

NGK? Really? You're gonna put rice junk in your American engine? You might as well put wasabi on your spaghetti while you're at it.

If it's not American, it doesn't go anywhere near my TJ.

Couple it with Borg Warner wires.
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Old 05-10-2011, 01:43 PM   #17
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Originally Posted by Jiffydarren
The following is purely the opinion of the user:

Don't put Autolite plugs in your Jeep. Autolite is made by allied signal, who makes Fram and Fram is crap. If you want a real spark plug, use Champion.

NGK? Really? You're gonna put rice junk in your American engine? You might as well put wasabi on your spaghetti while you're at it.

If it's not American, it doesn't go anywhere near my TJ.

Couple it with Borg Warner wires.
Haha wasabi on spaghetti =P ahaha!
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Old 05-10-2011, 01:49 PM   #18
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Originally Posted by Jiffydarren View Post
The following is purely the opinion of the user:

Don't put Autolite plugs in your Jeep. Autolite is made by allied signal
Right. Autolite's spark plugs are no more made by Allied Signal (who owns Autolite) than BFG tires are made by Michelin who owns BFG. Like BFG and their American made BFG tires that aren't made in France by Michelin who owns BFG, Autolite's spark plugs are made right here in the U.S. in the same Autolite plant and workers who were there before they were bought by Allied Signal.
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Old 05-10-2011, 01:52 PM   #19
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Originally Posted by Jiffydarren View Post
The following is purely the opinion of the user:

Don't put Autolite plugs in your Jeep. Autolite is made by allied signal, who makes Fram and Fram is crap. If you want a real spark plug, use Champion.

NGK? Really? You're gonna put rice junk in your American engine? You might as well put wasabi on your spaghetti while you're at it.

If it's not American, it doesn't go anywhere near my TJ.

Couple it with Borg Warner wires.
According to the NGK site...a good amount of their products are made in America, Corporate actually located in Irvine, CA with plants located in Irvine, California, Sissonville, West Virginia, and Chicago, Illinois. For future reference...autolite and fram are honeywell now not allied signal...


NGK Spark Plugs USA
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Old 05-10-2011, 02:11 PM   #20
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Champion. Change them every 30,000 or so for best performance. You don't need to buy expensive plugs or high octane gas.
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Old 05-10-2011, 02:44 PM   #21
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For future reference...autolite and fram are honeywell now not allied signal...
Yep you are right. I was thinking Allied Signal seemed wrong but I couldn't remember that it was really Honeywell both are owned by.
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Old 05-10-2011, 02:47 PM   #22
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Post #15 """""Thanks for all the help, after doing some research I went back with the NGK plugs, my Jeep has 88,000 miles on it and from the looks of the plugs I removed that was the first time they had been changed (had about a .80 gap) It ran good before the change but much better now, silky smooth. Hopefully my mileage will go up a tad! """""


Kinda shoots down the hype about using Autolite plugs designed for a PT Cruiser.

The under hood label was written by the people that made your engine. You'd think they'd know.

Honeywell no longer owns either Fram or Autolite. As with most flim-flam products, they get sold before the lawsuits catch up with them.

Check Wikipedia.
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Old 05-10-2011, 02:50 PM   #23
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Honeywell no longer owns either Fram or Autolite. As with most flim-flam products, they get sold before the lawsuits catch up with them.

Check Wikipedia.
Then why can you go to the honeywell website and go to their products and both fram AND autolite show up? Also the fram and autolite websites make note of a "honeywell car care product" at the bottom of their sites...

Wikipedia isnt the most reliable resource anyways...but in this case...check these out...honeywell

http://en.wikipedia.org/wiki/Fram_(oil_filter)

http://en.wikipedia.org/wiki/AlliedSignal
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Old 05-10-2011, 03:00 PM   #24
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Post #15 """""Thanks for all the help, after doing some research I went back with the NGK plugs, my Jeep has 88,000 miles on it and from the looks of the plugs I removed that was the first time they had been changed (had about a .80 gap) It ran good before the change but much better now, silky smooth. Hopefully my mileage will go up a tad! """""


Kinda shoots down the hype about using Autolite plugs designed for a PT Cruiser.
What shoots down the "hype" you claim there is about Autolite's plugs? Does he say he was using Autolite plugs? Nope so there is nothing about Autolite he mentions to "shoot down".

In fact, dual-tipped platinum plugs like the Autolite APP-985 and Champion 7034 perform extremely well in the newer DIS 4.0L engines and you aren't going to find any complaints about either plug in the new DIS 4.0L engine. Either would certainly last a lot longer than what he had in there and without any gap erosion.

If the OP installed conventional NGK plugs back into his DIS engine, he can expect them to need to be replaced much sooner than a plug better suited to the new DIS ignition systems would due to the DIS engine firing the plugs twice as often as in a conventional engine.

Sorry Rich but you're just spewing out a lot of outdated information and old wive's tales yourself. Like saying the most basic NGK spark plug the factory installs is the "best" plug to use in spite of better spark plugs being available that will outlast them by 3-4X. Recommending that plug just means you'll have to change it 3-4X as often. What spark plugs truly work well is a subject you're far more emotional about than factual.
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Old 05-10-2011, 03:58 PM   #25
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The Autolite plain 985's are made in China and the APP985's Mexico. I finally found some Champion 4412 truck plugs (I have a distributor), and they're made in the U.S. of A. I'm not sure if they were old stock, some say they're discontinued. My '99 loves 'em.
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Old 05-10-2011, 04:29 PM
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Wow!
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Old 05-10-2011, 05:05 PM   #27
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Wow!
Did you catch all that, mrclean ? We're gonna quiz you
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Old 05-10-2011, 05:37 PM   #28
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Jerry, youve been talking about the post 2000 engines. I've got a 1998 and I need new plugs soon. What kind do you think are best for my 4.0?
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Old 05-10-2011, 05:55 PM
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Did you catch all that, mrclean ? We're gonna quiz you
I'm trying to but I think I'm more confused now! LOL it's all good info and everyone has their opinions/ experience. The NGK's did well for 88,000 so I think I'll be safe with them, thanks again to everyone for their valuable input.
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Old 05-10-2011, 06:13 PM   #30
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Jerry, youve been talking about the post 2000 engines. I've got a 1998 and I need new plugs soon. What kind do you think are best for my 4.0?
Champion's 3034 and Autolite's AP-985 will both perform well in your distributor equipped 4.0L for over 100K miles. Both are single-tipped platinum plugs that work well in your non-fussy engine.

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