Need everyone's help again. I have a 90 Cherokee 4.0 4x4, thats giving me fits yet again. I have been dealing with a hesitation problem for about a year. I have another thread on this issue, which I need to update. Anyway, about the broken spark plug, this has happen twice. It starts running rough, acting like it was only running on 5 cylinders. Which has happened before, and same result. #1 spark plug broken. Hopefully the pic will load and see what Im looking at. Any advise would be great, and if you had the same problem, what fixed it?

 

That's bizarre! I've seen it before but it was just due to old plugs, not sure why you've had it happen twice. Are they the correct heat range for an XJ?

 

That is an interesting issue, only thing I could think of that is repeatable would be a heat issue, or the wrong plug. Just out of curiosity the wire is in good shape? Those pieces of the insulator probably aren't good in there though. It is the same plug as the other cylinders and installed at the same time?

 

I don't know about the heat range. Told the parts store I need plugs for my jeep. They a champion coppers, like everyone suggests on the forum.

Wires, plugs are all less then a year old. With my hesitation problem, I have replaced alot of stuff. YES, the broken peices worry me. The first plug did not beak, it cracked. This second plug broke. I would think I would really have a heat issue in the first cylinder, when all the heat is in the back of the 4.0. I dont know were to begin on this.

 

You aren't burning any oil by chance?

And is the dist/cap set properly?

I had this issue on an old F150 5.8L that would crack the insulation. Timing was not set properly. It would advance and run super lean.

 

Through the wonders of google I give you this

So you don't have to click: it suggests severe detonation, torqued down too hard or with the wrong tool, and incorrect gap settings.

The plugs you bought are pregapped correct, so probably not the issue. Torque/tool shouldn't be an issue unless you were having issues getting it in. I would lean towards the detonation, and the posts above seem to suggest that as well.

 

Show us a pict of the other side of the insulator. It looks "too clean" like it has a vacuum leak, making it run too hot.

Do a smoke test.

Is that the plug called out on the underhood label? Not the forum, not the parts druggie - the ones called out on the LABEL?

 

is that an auto lite spark plug? i only run ngk's or champions in the 4.0 motor

 

I am not burning any oil. Just my oil leak at the oil filter adaptor. Pretty sure my dist is set properly.


I found that too. Just a little confused on the severe detonation part? What cause that?? On installing the spark plugs, I am doing the same thing that I have been doing for years. First problem I have had with spark plugs.

Left the plug at home, will take a pic tonight. The plugs have less then 5000 miles on them. If I remember right. Everyone has told me the the champion coppers works best in the renix. But I do have an H.O. engine.


They are champions.

 

Sure, but which ones? There are lots of models and the 'parts counter druggies' (lmao) aren't exactly reliable. Doesn't look like RC12ECC like my '99 calls for, and I thought the RC12LYC looked similar. Aside from the NGKs these are the two most common plugs on the 4.0. (I may have the P/N slightly wrong as I'm on my phone)

 

You know what DOESN'T WORK. Now try what does!

Even if everyone else says different -
'everyone' did not design YOUR ENGINE.

If the label says NGK or grandma's molasses cookies - use it! Use the exact number and gap.

PREGAPPED PLUGS - always check them, 15% are gapped wrong.

Would you trust a pre-aimed bullet right out of the box to shoot a straw out of your mouth?

 

they look too long.

 

I understand I should use what the factory put in it. But like most older jeeps out there are muttS from different years. Sometimes you can't go off a label on the car when its not orginal. People have suggested the champion Coopers. I have tried them and so far are the best I have used in the past. Just have the #1 cylinder problem. Its a 90 cherokee, with a 95 4.0, with the 90 brains, and sensors. So I'm using the "trail and error" method.

 

"""""so far are the best I have used in the past. Just have the #1 cylinder problem."""""

LOL! I guess if you feel 5 out of 6 isn't bad, why did you complain here?

 

hows your fuel filter? been switched lately? tested fuel pressure at the rail?

that is usually what causes the engine to run lean unless maybe you have a bad intake gasket around the number 1 cylinder?

Definently looks like damage from the engine pinging.