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2000 is right about when Jeep made the switch away from a distributor and went distributorless. Does yours have the traditional distributor with ignition wires leading to each plug? This makes a major difference in what spark plugs to recommend.
 

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Discussion Starter · #3 ·
Gotta be honest not sure. I'm at work now but when I get back to my jeep I'll check and get back to you
 

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I have "coil rails" I guess. Are those difficult?
In my opinion, they are easier than wires. Remove 4 bolts and it lifts right off. I just replaced the plugs on my '02 and after finding what most recommend on here, I went with Autolite APP985.
 

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ah..I didn't have a problem with those either. The furthest one back..closest to the firewall was the trickiest, but I just had to put a wobble extension on the ratchet. Nothing seemed to be in the way. Took longer to make sure the plugs were gapped right then it was to do the actual change.
 

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Ok with the coil rail, that means your 4.0L is a little fussy about its spark plugs it will run well on. The Autolite APP985 and Champion 7034 are two good double-tipped platinum plugs that will perform well for 100k miles. The Autolite iridium-tipped XP-985 plugs will perform well for closer to 200k miles.

Never run single-tipped platinum plugs like the Autolite AP985 or Champion 3034, those will eventually cause a rough idle and misfires.

Single-tipped means the platinum coating is on just one side of the gap, double-tipped means the platinum is on both sides of the gap.

None of your plugs are especially hard to replace. :)
 

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For the single tipped spark plugs on a later model 4.0, will it cause idling problems immediately, will they show up after a short time (<10,000 miles), or does it only become an issue was you approach ~30,000 miles?
 

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It doesn't happen immediately which is why it took a while to figure out the random misfire/rough idle problem. Can't say exactly when it happens.
 

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When I reinstall my plugs I use about a 1 ft piece of rubber hose. Not sure of the size but its a snug fit over the end of the plug. This way when I screw it in via the hose there is no chance of cross threading. The hose has enough grip to screw it all the way in but not enough grip to damage the threads if it doesn't start straight. Then I just use the wrench to snug them in place.
 

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When I reinstall my plugs I use about a 1 ft piece of rubber hose. Not sure of the size but its a snug fit over the end of the plug. This way when I screw it in via the hose there is no chance of cross threading.
Another way to do this--which I learned from a mechanic--is to use a universal joint and thread each plug by hand. This allows you to still use a spark plug socket (which was specifically designed to hold onto the plug while it is being inserted) and it prevents you from cross-threading it. I will attach a 6" extension to the universal joint, and that's my 'handle' for inserting the plug.
 
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