Explain if you will. I'm stumped on what you mean.

 

Use one of these wire type gapping tools to check/adjust the plug gap to .035".



Do not use one of those coin looking things, and don't use feeler gauges.

Don't put Dielectric grease all over the plug connectors in the coils, and don't put it on the plugs. Use Dielectric grease to cover the inside surface of the plug boots only, applied with a Q-Tip.

Do not use anti-seize compound on the plug threads. And remove any residual anti-seize compound from the threads in the head. Torque the plugs to 27 ft./lbs.

 

Holy crap! I have to chuckle when I see multi-page write ups on the subject of motor oil and spark plugs in these forums. The depth of analysis and debate over these simple items suggests that some ppl really have nothing better to do in life. I drive my XJ and perform routine maintenance without fretting over the rotella factor or champion versus NGK and..... Know what? It runs perfectly. It's not this complicated folks! It's an old AMC. They are simple machines!

 

For some Cherokee owners this is their first rodeo and ask for guidance. For others, they just like to get their licks in.

Glad to see you are a big man on campus.

 

Its not about over analysis. Its about learning more about the products we use. There's a lot of people that wanna know what they're putting in their rig, and there's a lot of people that would like to voice their opinion on the products that they've used. Now of course there's people out there that are gonna bash others or voice their opinion on something they've never used but that'll happen anywhere. It's also not about getting people to switch products or whatever, its meant to spread facts.

 

Ask this guy

 

Sure you didn't get a wire crossed up?

 

The place where you measure to make sure the gap the little white piece I want the say the insulator is to entirely different lengths and to answer other is , it's a coil pack set up so no wires

 

Impossible if you have the exact same spark plugs.

Can you take a photo of the different spark plug center electrodes and post them here? Sure would help.

 

Okay I took out one spark plug to show what I mean.

 

Which plug did you take out to show what you mean?

You'll see that the RC12ECC plug and the ZFR5N plug is almost identical, and that the RC12YC plug center electrode insulator is much more inset than the RC12ECC plug, even though both plugs are the same heat range.

RC12YC plugs are absolutely wrong for a your 2000 engine.

You can use RC12ECC plugs or NGK ZFR5N plugs in your engine, but Chrysler has switched to using the NGK ZFR5N plugs in the '00-'01 engines. If you went to the dealer and asked for a set of plugs for your engine they would more than likely hand you a set of ZFR5N plugs.

The RC12ECC plug and the ZFR5N plug are almost the same heat range. The ZFR5N plug has a slightly cooler heat range than the RC12ECC plug, which may be why Chrysler went with them. The coil rail "waste spark" ignition system fires the plugs twice as much as the conventional distributor ignition system, so the life expectancy would be less.

The plugs fire in sets, once while on the power stroke of a cylinder and at the same time on its companion cylinder on its exhaust stroke. I think this was Chrysler's attempt to address heavier EPA emissions requirements.

These are the companion cylinders.

1 - 6
5 - 2
3 - 4

No matter which plugs you select (RC12ECC or ZFR5N) make sure they are all (6) a matched set. Do not mix plugs.

Do not use those E3 plugs.

If you have rough running problems with a matched set of the recommended properly gapped plugs you have other problems. Coil Rail, combustion chamber problems, valve problems, or vacuum leaks.

 

So my question comes up again... Why does it misfire with those longer plugs but not with the rc12yc ones? I'll try gap checking the NGK ones tomorrow and throwing them back in to see if it helps at all. Another quick question is how do I see if the engine has been swapped out, is there a way to find out if the engine is the still the same original one for the jeep cause when I talked to a parts store associate they told me the plugs I'm using are the ones British people use in there 4.0 I6, I'm currently stationed in England. Plus with the longer ones do I need to worry about them hitting the piston

 

If your engine is orignial 2000 4.0 (we are talking about a 4.0 liter engine aren't we?) it would come with a cylinder head with a casting number of 0331. The pic below shows the location of the casting number, left side of head.



I just took another look at those plugs. I looked up RC12YC on the Champion website and it shows those plugs used in a bunch of foreign autos, not the Jeep.

Champion RC12LYC plugs were used in the 4.0 before Chrysler switched over to RC12ECC plugs. The 12LYC looks almost identical to the 12ECC.

By the looks of that RC12YC plug it looks fouled. Were all the 12YC plugs fouled like that?

Some people use "Anti-Fouler" devices to draw the plug further out of the cylinder when they are having fouling problems. That 12YC plug looks like it was acting like an Anti-Fouler by pulling the electrodes further away from the combustion chamber.

At any rate, the RC12YC plugs are not for your engine, regardless of what the Brits use.

If you are having fouling problems (misfires) you may want to run a can of combustion chamber cleaner, like Seafoam, through the engine to see if the combustion chambers can be cleaned out.

 

I wish I could use the sea foam here but they have laws here against that... Brits are dumb about car laws and what not, I'm going to give the NGK a shot again and make sure the gap is perfect on each one before install them. I'll be back in the states in less then 2 months. And yes all the spark plugs looked identical to one another. I'm going to take a bunch of pics for ya to see if anything sticks out to ya. Thank you so much for all the help tho I truly appreciate it

 

Some people have dribbled water through the throttle body to clean out their combustion chambers. The process is argued like which oil to use, etc. If you do a search here, or Google it, you can find out how to do it.

Brits don't have an objection to water do they?