xjJaceM

I have an '01 Cherokee Sport 4.0 straight 6. it's been running rough for about a month or so now. I ran the codes and I have a misfire in cylinders 4, 5, and 6. I replaced the plugs and the boots and I still have the same problem. I want to say that it is the ignition coil, but I don't want to throw out $110-150 if that isn't the problem. Any suggestions on what else could be causing this problem would help a lot.

Thanks, Jace

4WD4EVER

Be sure to have the correct spark plugs in it first, then read this:

http://www.naxja.org/forum/showthread.php?t=938256

Edit: Welcome to the forum, btw.

Programbo

I know some of the newer ('99+) XJs had a "heat soak" problem where the heat from the exhaust manifold would affect injector function. But I am thinking that just applied to one injector? Maybe someone else can provide more info on this specific problem I am thinking of.

4WD4EVER

After you make certain you have the recommended plugs in it and check the coil (which I don't think is the problem), I think you need to check the cyl. head casting #. Here is some info on that:

https://www.cherokeeforum.com/f2/00-...erview-118922/

Let us know what you find.

Also, what are the specific codes being thrown?

xjJaceM

I forget which spark plugs exactly I put in them, I want to say I put Champion Double Platinum. it's been about 3 weeks since I changed them and the exact brand is slipping my mind. What kind of plugs would be the exact ones? I have a buddy who works at O'Reilly and I went in there and he did a computer search and these were the "preferred ones" I just don't know what exactly it is. My check engine light is on all the times but after 20-30 minuets of driving it starts flashing and it takes 2-3 seconds to accelerate after I hit the gas, almost like a sputter.

4WD4EVER

If I were you, just for the sake of getting it correct, I would go with the OEM plugs (at least for now). Should be plain, old Champion copper. IDK the exact # for your MY, you'll have to ask/look up.

Read the other link I provided on the cyl. head casting before you throw more time/money into this. Then go from there.

Edit: IDK, someone else will have to chime in. Maybe the platinums are the preferred plug for it.

xjJaceM

I don't have coolant loss at all, code P0305

xjJaceM

Thanks for the help a lot, I'm going to try and mess with it some more and see if I can find something out.

4WD4EVER

You're welcome. Let us know what you find out from the coil test.

Edit: A cracked head can cause the symptoms and throw the code you're describing. Just keep that in mind. I'm not saying that's it or not.

4WD4EVER

Just found out that if you buy spark plugs from the dealership they will sell you NGK ZFR5N spark plugs. These are nickel plated, not platinum. These are the OEM replacement of the Champions. You may want to consider swapping out the platinums. Your call.

Firestorm500

Every 2000-01 XJ 4.0 has a known factory casting flaw in the head.

It cracks, usually between #3 and #4.

Your diagnostic path may eventually lead you to this. I don't think a minor variation in plug type is going to cause your problem.

4WD4EVER

Yes, if I had this MY I'd want to verify compression as a preemptive measure. Coolant loss or not.

As far as the plugs go it has been documented by CF member "noredplz" that the incorrect plug is known to cause misfire/runnability issues. I would think it best to rule this cheap possibility out.

OP, after you've checked your coil for peace of mind, I would get all of the engine/battery grounds cleaned up well. Here is a link to assist you with the locations:

https://www.cherokeeforum.com/f2/eng...130071/index2/

Then, I would check the CKP (crank position sensor). Here is a link for that:

https://www.cherokeeforum.com/f51/testing-cps-5563/

CCKen

Coil Rail test:




Usually if one coil is bad it will affect companion cylinders.


1-6
2-5
3-4
.

xjJaceM

Thanks for the diagram, I will try testing the coil rail when I get home this afternoon and will see how it goes and update it.

Firestorm500

Platinums work flawlessly in my '87 and '92 4.0s. Why would they not work well in a later model?