I purchased today an 01 Cherokee Sport with a 4.0L & auto tranny. It has almost 100K and appears to have been well maintained & treated kindly. I intend to use it gently to go up in the mountains in FS roads, go fishin & and the occasional trips to town. I haven't had a Jeep in 20+years, just Dodge Cummins HD Trucks w/ manual trannys, so I am a little out of touch about gas engines, tires, auto trannys, etc. Any help from you knowledgable XJ guys would be very helpful. I will buy a Haynes manuel tommorrow.

#1-The rig could use new rubber. The stock size is P225/75/15. Do they make an LT235/75/15 and are these any better (or worse) as a replacement? What tire size would you recommend?

#2-I dont see any spark plugs on a cursory inspection...where are they hiding on this 4.0L? Can I use Platinum plugs ? What is the correct gap setting?

#3-Anything I should know about this particular rig/year? Any known weak links? Good points?

#4-What spare parts/fluids/tools do you routinely carry onboard?

Thanks in Advance, Steve in Durango, Colorado

1. For a stock rig the 235/75/r15 tires are going to be your best bet.

2. in 01 the 4.0 had a distributorless ignition so the plugs will be under the coil pack. The correct gap size will be under the hood.

3. On your rear axle below the pumpkin is it flat or rounded with corners? Also your rig has a LP d30 which is less desireable when you are lifting it.

4. I carry a socket set, breaker bar, torque wrench, misc tools, batter jumper, 2 tow straps, flares, 2 flashlights, greese, ATF3, and a couple courts of 10w30.

Thanks, Kyle for your help. Is the tire size you recommend a "P" or "LT" type tire. I assume an LT tire will have a beefier sidewall & casing, if it is available or even recommended ???

Is a distributorless ignition a bad thing? I am guessing those 6 little wires with the funny thingy on top is the coil packs. Are they easy to remove?

P and LT is this brand specific? Like tread types?

I think he is referring to P = Passenger and LT = Light Truck.

Correct, Do not run platnum plugs, Jeep design there coil packs as a low voltage system. Run a standard Champion plug and 89 octane fuel.

Thanks for the flow of info. I have run (and am running) Dodge HD trucks with Cummins diesels for the last 10 years, so I am way out of touch with gas engines, auto trannys, fuel types, tire sizes, etc. That may explain some of my ?

Yeah, I meant a pax car tire vs. a light truck tire. Do most of you run LT's? 6 ply ratings?

So, no long life plugs....just the standard old style metal tip plug?? Damn. Any others work, such as the Champion "copper" or ?? Most of our gas here is rated at 87 or 88 octane due to the altitude (7,000')....is this O.K. or does it need the extra octane for anti knock, etc?? Can a bottle of fuel injector cleaner be added to the fuel every once & awhile or does this cause havoc with sensors, etc??

Does the 01 with coil packs over plugs have any issues I should be aware of with these coil packs? Are they O.K. or poison?



Thanks, Steve

sorry jeff, i refuse to run champion plugs...lol

i normally just run 87, unless i'm wheeling..then i run 93. seems to run better at 5,500rpm on 93

never had any problems with my '00. just be careful pulling the coil pack rail off.

Coil packs are fine. Run a copper plug and low octane fuel. The higher octane for a DD makes them run bad. When I wheel I mix a half a tank of 88 and 93. Oiradio suggested that to me and it does work.

More ????? Thanks, Guys for the info so far.
These mysterious coil packs of which you speak......must be the assemblies that are where I think the spark plug should be.
The Haynes manual doesn't even mention them, and I will be VERY careful the first time attempting to pull them off for a plug change. A very small guage wire running to the coil pack....I am not a mechanic, so is it a low amperage/high voltage current that runs to these things & then gets boosted by the coil pack so the plug will spark?? What determines when each plug gets a jolt of electricity if no distributor.....the engine management computer?? Do you need to carry spare coil packs in the field, or are they durable??

the coil pack is a pain in the but. especially when you get to the back by the firewall. i run 87 in mine as a DD and it runs great. when on the trail i run 89-91 just so it doesnt get carbed up.

It would be a good idea to have an extra coil pack but they are pretty expensive and very durable. The engine management computer is what controls their firing w/o a distributor. Most people don't carry a spare coil pack. When a prior poster said they don't run Champion plugs that is not the consensus of most XJ 4.0L owners. I have had several different XJs since about 1990 and have done some experimenting. Champion copper truck plugs work the best and last longer than any other I have tried. The closest second was NGK plugs.
As to the transmission, it is bulletproof. Change the fluid as recommended by the owners manual and use only Dextron III in it. Do not listen to the idiots at most dealers, they say that ATF3 is the same but it is NOT. Use what it was designed to use Dextron III.
Getting down off my soapbox now!!!

AC delco plugs and the best 87 money can buy. But I have a GM motor.

I agree, use the Champion truck plug and i wouldnt really worry about the extra coil pack. They are very durable. And yes they are a pain in the butt to get off.