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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Any idea what may have caused this? I did trickle 32oz of water through the engine a few weeks ago. I had inspected a couple plugs a few months ago and didn't have the cracked electrode ceramic at that time. Looks like I've had a few chunks of ceramic material run through 4 of 6 cylinders.
You should try using the plugs recommended by Chrysler = Champion RC12LYC, gapped to .035".
Originally Posted by cruiser54
ZFR5N NGKs
Here are two forum heavyweights giving apparently conflicting advice. Fight! Fight!
My understanding is that '99 and earlier XJs prefer the Champion plugs, while '00 and '01 came with NGK plugs and do better with those because of the distributorless ignition system. So the correct answer in this case will probably depend on the year of OP's Jeep.
Here are two forum heavyweights giving apparently conflicting advice. Fight! Fight!
My understanding is that '99 and earlier XJs prefer the Champion plugs, while '00 and '01 came with NGK plugs and do better with those because of the distributorless ignition system. So the correct answer in this case will probably depend on the year of OP's Jeep.
Ken is using the application chart. I'm using experience.
I use those NGKs in
EVERY 4.0 of mine and when I do tune-ups for customers.
Chumpions may work well now, but certainly no better than NGKs.
In almost 50 years of working on cars, I have never had an NGK fail.
Platinums numerous times, Champions were such a problem at the time I was at the dealership, we used
ACs.
Ever wonder why they went to NGKs on a high demand application?
Think about it.
Below is a spark plug application chart I put together. The plug numbers come from the Champion, NGK, and Mopar catalogs.
Also, a Tech Tip document from Chrysler showing the RC12ECC plug replacement using the NGK ZFR5N plug.
My emissions decal on my ['99] firewall shows Champion RC12ECC plugs recommended, but I have used the NGK ZFR5N plugs for a few years now with no problems.
I wouldn't be afraid to use the NGK ZFR5N plugs in the '91-'98 4.0 engines but I would be a little nervous about using them in the '88-'90 4.0 because of the original heat range plugs used in these years.
Chrysler switched to the RC12ECC plugs because of a seemingly superior plug design, where the "CC" stands for Copper Copper; that is, the center and ground electrodes are both Nickel plated Copper. The switch to the NGK ZFR5N plugs was justified thru field use in the waste spark ignition system, where each spark plug fires twice - once on the compression/power stroke and simultaneously on the exhaust stroke of the companion cylinder (1-6, 5-2, 3-4). The plugs get a work out in these applications, and apparently can last longer in service. I don't have a 2000/2001 Owner's Manual so I don't know the recommended plug replacement interval but my '99 manual states to replace them at 30,000 miles (RC12ECC Plugs). The NGK ZFR5N plugs should last a bit longer but I'm not going to push it.
Chrysler switched to the RC12ECC plugs because of a seemingly superior plug design, where the "CC" stands for Copper Copper; that is, the center and ground electrodes are both Nickel plated Copper.
01-22-2017, 08:22 AM
Ugly plugs, what causes this?
