So ZFR5N is the correct part number. I think I found them through Nappa, they're a tab more expensive.

Let me know if these are the correct plugs:
http://www.napaonline.com/Catalog/Ca...252_0275416539

Also, what are some other performance symptoms related to detonation? I haven't really noticed anything out of the ordinary besides a broken spark plug.

 

Negative - 7252 is FR51. You want 3459. They're $2.01 each on RockAuto.com

 

Probably just a faulty plug.

Find a shop nearby that works on European cars and get yourself a can of BG 44K. Add the contents of that expensive can to a full tank of gas and run it down to 1/8 tank. It will clean out carbon deposits, clean the injectors and valves.

 

Thank you for verification.

 

How old are the cap, rotor and wires?

 

I'll check the cylinder 6 plug again in a few 100 miles. If it's a reoccurring problem by then, I will switch to the NGK plugs. The fuel additive is damn expensive... You sure it's not snake oil?

 

Faulty plug. It happens. I had the same thing happen in the wife's Yukon. It was only two years old and threw a misfire code. Guys at the parts store didn't think it could be a plug because it was such a new car. But I bought a new set of plugs anyways as the cheapest 1st option. Turned out the porcelain jacket was cracked. Looked just like that.

 

Absolutely NOT snake oil. I've used it for years. Just do the NGKs.

 

I did cap and rotors with my prior tune up, last April. I've only 4k on them though. They were the Echlin/Belden parts via NAPA.

Also, NGK #3459 is not being shown on RockAuto. Only NGK #7252. I'm driving a 98.

 

Wires? Just go into Napa and get the NGK plugs.

 

The wires were Belden. Done with the tune up last April. I've contemplated changing them. They looked a bit black when peering down into the tube.

 

Wires should be good for 30,000 miles. Especially belden.

 

I'll run the Champions for a while and see how things work out. If the issue continues, I'll do the switch.

As for the tapping I'm getting. I don't think it's caused by detonation. I could be wrong. I'm running MMO in it now. If that doesn't quiet things down I'll look to pulleys, and flex plate. Sounds like it's coming from the back of the engine though. Not a pulley. As for that expensive can of fuel system cleaner, I'll see where I can find it.

 

good champions come in jeeps from the factory till this day.

 

Don't procrastinate on those flexplate bolts. Just flat do them.

That 44K only needs to be done once a year. Extremely effective.

As for the plugs, I don't see the logic in keeping things inside my engine that have already proven to throw chunks of porcelain in to it. For $12? Not me.

https://www.cherokeeforum.com/f51/ho...ocking-125547/