What are the best spark plugs for my Jeep Wrangler TJ 4.0?

I wouldn't use those Bosch plugs in a TJ engine. The best choices are the factory specified NGK ZFR5N plugs or if you only want to change plugs every 60,000 miles rather than every 30,000 miles you can spend approximately twice as much and go with double platinum plugs such as Autolite APP985 or Champion 7034.

Personally, I don't see much point in spending the extra money for double platinum plugs. They do not provide measurable performance benefits over the specified NGK ZFR5N plugs and since I typically pull the plugs to check their condition at 30,000 mile intervals anyway (every 3-4 years based on my jeep usage) I might as well install fresh plugs while I'm at it.
 
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I went to a local parts store to get same new plugs for my 2005 unlimited. I had asked at a local off road shop what brand plugs they recommend and was told Champion. Not know what number plugs to ask for the store sold me the Champion 9034. I see on here the recommend ones are 7034. Has anyone used the Champion 9034 plugs?
 
Champion 7034 plugs are platinum; 9034 are iridium. Platinum plugs are reputed to last 60,000 miles; iridium 90,000 miles or more. The difference between these and the factory recommended NGK plug is primarily longevity, not performance.

As noted above, I stick with the factory specified NGK ZFR5N spark plugs and change them at the recommended 30,000 mile interval. The cost per mile is approximately the same as with the more expensive platinum and iridium plugs.
 
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Champion 7034 plugs are platinum; 9034 are iridium. Platinum plugs are reputed to last 60,000 miles; iridium 90,000 miles or more. The difference between these and the factory recommended NGK plug is primarily longevity, not performance.

As noted above, I stick with the factory specified NGK ZFR5N spark plugs and change them at the recommended 30,000 mile interval. The cost per mile is approximately the same as with the more expensive platinum and iridium plugs.
 
Thanks Bills, There so much info out there on plugs and the 4.0. Nothing wrong with changing every 30k. But I like the idea of getting a plug that lasts longer........just in case I get lazy at the 30k mark. As I mentioned I'm running the Bosch plugs. But based on your advise and the advise of others, I plan to pull them and replace as suggested. Maybe I'll even see a preformance differnce?
 
Thanks Bills, There so much info out there on plugs and the 4.0. Nothing wrong with changing every 30k. But I like the idea of getting a plug that lasts longer........just in case I get lazy at the 30k mark. As I mentioned I'm running the Bosch plugs. But based on your advise and the advise of others, I plan to pull them and replace as suggested. Maybe I'll even see a preformance differnce?
Bosch has a great reputation for fuel pumps here but not their O2 sensors or spark plugs. The problem with their plugs is they don't usually work all that well in our Jeeps and a Bosch engineer once opined that it's due to Bosch's more limited range of available heat ranges when compared to larger spark plug manufacturers like Champion, Autolite, or NGK.

Personally Mcoh I'd go for the Autolite XP-985 which is iridium tipped, which is what I switched to 7-8 years ago. A friend at Autolite had his put under their electron scanning microscope at nearly 200k miles and they detected no wear or erosion of the iridium coating. He said based on that they're not even sure yet what their ultimate life will prove to be. For those who think they might seize being in that long, just careully apply a little dab of antiseize to the spark plug threads before hand-threading them in. Make sure not to get any of the antiseize on the electrodes.

Or the Champion 7412 (edit: replaces the Champion 7034)
tor Autolite APP-985, both of those are platinum tipped and good for 100k miles. :)
 
Bosch has a great reputation for fuel pumps here but not their O2 sensors or spark plugs. The problem with their plugs is they don't usually work all that well in our Jeeps and a Bosch engineer once opined that it's due to Bosch's more limited range of available heat ranges when compared to larger spark plug manufacturers like Champion, Autolite, or NGK.

Personally Mcoh I'd go for the Autolite XP-985 which is iridium tipped, which is what I switched to 7-8 years ago. A friend at Autolite had his put under their electron scanning microscope at nearly 200k miles and they detected no wear or erosion of the iridium coating. He said based on that they're not even sure yet what their ultimate life will prove to be. For those who think they might seize being in that long, just careully apply a little dab of antiseize to the spark plug threads before hand-threading them in. Make sure not to get any of the antiseize on the electrodes.

Or the Champion 7034 or Autolite APP-985, both of those are platinum tipped and good for 100k miles. :)

What should the gap be set at for the Autolite xp-985?
 
This question comes up often, so I figured it's time for a FAQ on the matter.

The later model 4.0 engine (2000 and later) is what is known as a DIS (Distributorless Ignition System) which is far fussier about what spark plugs it likes to run well on. A DIS ignition system also fires the spark plugs twice as often which means a conventional copper-core spark plug only lasts half as long in this type of engine. All 4.0L engines that are 2000 and newer have the DIS ignition system. 1999 and older 4.0L engines aren't nearly as fussy so long as they are the right model plug. 2000 and newer 4.0L engines won't run well for long on single-tipped Platinum plugs, even though some catalogs show them as an acceptable plug. So do avoid any platinum plug that only has platinum on the center electrode.

I always recommend dual-tipped Platinum or Iridium spark plugs which will perform well for at least 100K miles. Iridium tipped plugs will last significantly longer than even the 100K miles dual-tipped platinum plugs will.

Good dual-tipped platinum plugs include the Autolite APP985 and Champion 7034. The NGK 7866 laser iridium spark plug is also a good choice as well.

A good iridium tipped plug for the 4.0 engine would be the Autolite XP985. A technical trainer at I know at Autolite checked his iridium plugs at 165K miles and they showed no visible wear.

Such plugs last so long that it's a good idea to smear a dab of copper-based antiseize onto their threads before screwing them into the head. Make sure no antiseize gets onto the electrodes (tip).

So while conventional plugs are what the factory installs and they are the cheapest, that doesn't mean they are the best choice for replacement spark plugs.

As always, great advise, thanks Jerry!!!!
 
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Has anyone used the Bosch Platinum Plus 2 Plugs? I've been using them for the last 80k miles. No issues. Pulled one the other day....some carbon deposits....but that's it. Thinking of going for them again, as they are No Gap. Any comment/suggestions on this subject would be greatly appreciated.

Also, when speaking of Plugs, how about the Coil Rail? How long before it should be replaced???
I like to not gap lol. Last plugs I changed was on Chrysler T&C and I bought my plugs from Autozone and I asked about gapping then and he said no don't worry about it. I can't remember if they were bosch or champion
 
So @Jerry Bransford , are iridium plugs good for all Tj's? Would that be good for my 98 4.0L? I've never really changed plugs unless I came up with a misfire in any of my vehicles. But what I think I'm learning here is iridium plugs will last almost the lifetime of the vehicle?
 
So @Jerry Bransford , are iridium plugs good for all Tj's? Would that be good for my 98 4.0L? I've never really changed plugs unless I came up with a misfire in any of my vehicles. But what I think I'm learning here is iridium plugs will last almost the lifetime of the vehicle?
Yes the XP985 would be a good choice for any of the 2.5L or 4.0 engines in our TJs. Autolite knows from testing it's good for at least 200k miles. :)
 
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I like to not gap lol. Last plugs I changed was on Chrysler T&C and I bought my plugs from Autozone and I asked about gapping then and he said no don't worry about it. I can't remember if they were bosch or champion
Just an anecdotal experience but when I got my autolite plugs from Amazon I had to regap all of them. Not hard at all to do though.
 
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I know the process. Years ago I use to use the round coin gapper. I think now a days you don't have to regap If you don't want to. However I have not used autolite. More champion and possibly bosch.
Just an anecdotal experience but when I got my autolite plugs from Amazon I had to regap all of them. Not hard at all to do though.
 
Ok, I'm going to pull the trigger on the AutoLite XP985 Iridium Plugs. They're expensive, but I'm certain, based on the reviews on this post, my own gas mileage and performance that once I make the change I should notice a difference.

Here's the question; in an earlier Post on this Thread, there's mention of gapping the plugs. Now supposedly, the Autolites come "Pre-Gapped". But I'll be damned if I trust them to be gapped correctly. So because their Iridium is it possible to use a Gap Tool like this; Without damaging the Plug and if so, what's to proper technique if any to increase/decrease the gap?

Thanks!!!



gap tool.jpg
 
What would you suggest for spark plug wires?
For your 2001 Sahara? Are you sure you have individual spark plug wires coming out of a distributor cap and not the newer coil plug rail that sits on top of the spark plugs?

If you have an early 2001 with a distributor cap, go for OE Mopar ignition wires if you can find them. Make sure to avoid the multitude of "performance" spark plug wires pushing "low resistance". While low resistance wiring sounds good, it's not where the ignition wiring is concerned. In fact, resistance is intentionally added to the ignition wiring at extra cost to stop them from emitting a static RF signal that can disrupt the engine computer as well as cause static on your AM or CB radio.
 
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For your 2001 Sahara? Are you sure you have individual spark plug wires coming out of a distributor cap and not the newer coil plug rail that sits on top of the spark plugs?

If you have an early 2001 with a distributor cap, go for OE Mopar ignition wires if you can find them. Make sure to avoid the multitude of "performance" spark plug wires pushing "low resistance". While low resistance wiring sounds good, it's not where the ignition wiring is concerned. In fact, resistance is intentionally added to the ignition wiring at extra cost to stop them from emitting a static RF signal that can disrupt the engine computer as well as cause static on your AM or CB radio.
Jerry I’m going to be honest with you....I don’t have a damn clue. Haha. I know that I want to replace the spark plugs and do my own little tune up kit so I was just tying to get as much knowledge as possible to see what I should get. I was thinking AE Delco air filter, spark plugs that you suggested in this thread, wires? If needed, sounds like not, oil filter and whatever you’d suggest master Yoda. Haha.
 
Jerry I’m going to be honest with you....I don’t have a damn clue. Haha. I know that I want to replace the spark plugs and do my own little tune up kit so I was just tying to get as much knowledge as possible to see what I should get. I was thinking AE Delco air filter, spark plugs that you suggested in this thread, wires? If needed, sounds like not, oil filter and whatever you’d suggest master Yoda. Haha.
Post a photo of the passenger side top of your engine so we'll both know what you have ignition system-wise. :)