What Happened to my Jeep!!!

I have a 2000 Jeep Cherokee Sport 4.0 129,000 miles and I purchased it back in December for all this snow we got in VA. Anyway it ran and sounded great, it was previously owned by a mechanic and here we are....

Recently I have noticed an intermittent hollow knocking sound until it gets warm which sound like piston slap, I just noticed that two weeks ago. Next, it has gotten warmer and now after driving a sustained amount of time and getting the engine and engine oil hot, I shut the Jeep off and when I turn it back on with the engine still warm there is a crazy hesitation and miss going on. Now The check engine light came on soon after this today and I took it to Autozone and diagnostic said cylinder #3 is misfiring.

What the hell happened to my Jeep all of a sudden. I check fluids more often then I should. I changed the oil when I got it and after 3000 miles on the dot. It was overfilled by about half a quart for 300 miles but I quickly drained it out after I noticed. I used Castrol 10w-30 and Federated Auto oil filters (like NAPA). Any advice please so I can get this figured out.... Thanks

Your check engine light and hesitation are due to "Heat soak". Basicly a design flaw for the years 200/2001.

The only real cure is to install a timer so that when you shut the rig off the fan will run for a little and cool off the engine. In the meantime, when ever you stop, open the hood. It will help with the heat, which is due to the extra catalytic converters used by Jeep to help it pass emmisions for that year.

Your other engine noise/overfull oil might be due to the dreaded "0331" head. Which is prone to cracking.

I own a 2000 and am about ready to light it on fire. Do a good search on these problems, lots of threads in this board about them. Good luck with it.

some guys have had good luck with hood vents. it lets out some of the extra heat from the two pre-cats on the exhaust on the 00-01 xjs. many use hood vents out of a le barron but i went with vents off a chewy lumina z34 on my 95 xj

Ok, I'll have to try the hood vents. I've read a lot about the piston slap which seems normal on these 4.0's and considering my step dad's knocks like crazy at start up but runs all day with 200K on it. I'm not too worried about the knock, but am now wondering why it started now? Any responses to that?

aeg1212aeg said:

Ok, I'll have to try the hood vents. I've read a lot about the piston slap which seems normal on these 4.0's and considering my step dad's knocks like crazy at start up but runs all day with 200K on it. I'm not too worried about the knock, but am now wondering why it started now? Any responses to that?

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If I had a nickel for every time someone said "it just acted up out of the blue!" It's like people think their Jeep's supposed to email them a pending failure notice a week before it acts up or something. It doesn't matter why it started now, but realize you've only had it for a few months so you don't really know what is normal for that particular vehicle through the seasons.

Hood vents, easy and cheap. one day, and about 10 to 15 in supplies. Here is my thread:

http://www.naxja.org/forum/showthread.php?t=1018569&highlight=hood+vents

There is a link I refer too in the first post. Look at that too. He lists the materials. Best of luck to you!

Also to consider, wire up a switch for the electric aux fan could help. I ran a typical (i think its a) 30amp fuse/relay under the hood and switch inside the cabin. I did this mainly cause when the compressor kicks on, it too ran the fan, but for only as long as the compressor ran. Its loud and annoying to have that keep kicking, and I wanted to control it haha. I have no heating issues. I run the fan when im wheeling... slow speeds with lots of work on the motor requires some help. Willam mentioned a timer. Maybe you could incorporate that into a switched circuit, that way when you know you will be firing it up warm, you can leave the switch on, and let timer shut it off. Either way, it will kill the fan after a certain time, so it should not drain your battery if you left it on all the time. Just some thoughts.

The cylinder #3 misfire and engine stumble upon hot restart fit the TSB perfectly. I've enclosed a copy of it below. As mentioned, the "factory" fix of putting a heat shield on the #3 injector isn't the best. I think they spent all of 20 minutes coming up with that lame-o fix. Most guys go with vents, e-fan mods, etc. SEARCH.

The noise could be a bit of a lifter noise. Drive it for a while. The 4.0 isn't a particularly quiet engine for some. If the noise doesn't change and you are keeping up with your oil changes, this noise can be thought of more as a "characteristic", than a problem.
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TSB
1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supercedes 1802702 dated 09/06/02)
Model Year(s): 1999-2004

Description: NOTE: This bulletin applies to vehicles equipped with a 4.0L engine. This bulletin involves the installation of a fuel injector insulator sleeve.

Details: Customers may describe a 20 to 30 second rough idle following the restart of a heat soaked engine. This condition may be most noticeable when the engine is restarted following a prior 10 to 20 minute heat soak in hot ambient conditions of approximately 32 C (90ºF) or higher. This condition may be consistent with short city stop-and-go driving trips and can be aggravated by the use of fuel with a high ethanol content. Depending upon various conditions a MIL may occur due to DTC P0303 - Cylinder #3 Misfire.

This condition may be caused by heat from the exhaust manifold that following engine shut down migrates to the area around injector #3 and causes fuel vapor to form within the injector. This in turn may cause a momentary misfire of cylinder #3 until the fuel vapor is cleared of injector #3. The insulator sleeve lowers the injector #3 temperature to a point below which the fuel will not normally vaporize.

If vehicle exhibits a rough idle, and if a misfire of cylinder #3 is observed following a 10 to 20 minute hot soak, perform the Repair Procedure.

Parts required:
56028371AA Ignition Wire Shield

Repair procedure:
1. Cut insulator sleeve, p/n 56028371AA, to make two (2) insulator sleeves about 25-30 mm (1 in.) in length. See diagram.
2. Install one sleeve around injector #3, with the slit on the upward facing side of the injector. Install the other sleeve with the slit on the downward facing side of the injector.
3. Confirm sleeve is flush to intake manifold surface around injector.
4. Check injector #3 wire and ensure that the injector is rotated to a 2 o'clock position.

You've been given some good advice here. Might I suggest also checking your flexplate bolts to see if they're loose if you have an automatic transmission?

Just to be safe I would send an oil sample to Blackstone Labs, best $20 you'll spend.

Finding more fluid in the oil pan, rod knock, and 2000 XJ all point to the dreaded 0331 head crack failure. Coolant in the oil attacks the rod and main bearings. Start keeping tabs on coolant levels and as recommended--send an oil sample to a lab to get diagnosed.

JJacobs said:

If I had a nickel for every time someone said "it just acted up out of the blue!" It's like people think their Jeep's supposed to email them a pending failure notice a week before it acts up or something. It doesn't matter why it started now, but realize you've only had it for a few months so you don't really know what is normal for that particular vehicle through the seasons.

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Cool.... Best advice ever, Anyway I will check the flexplate bolts and I keep up with the coolant level and it is always at the neck, I just think the noise is characteristic. Anyway thanks everyone

gradon said:

Start keeping tabs on coolant level

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Good advice. The biggest clue to the cracked 0331 head is when the coolant level in your reservoir starts to drop......it could be going into your oil.

When checking the collant level, always do it from the bottle. When you open the radiator cap your just letting air in the system. Natural expansion/contration will be regulated by the overflow bottle. Check the level there when the engine is stone cold, it will be your best indicator.

willam said:

When checking the collant level, always do it from the bottle. When you open the radiator cap your just letting air in the system. Natural expansion/contration will be regulated by the overflow bottle. Check the level there when the engine is stone cold, it will be your best indicator.

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I prefer to remove the radiator cap when the engine is 100 percent cold to make sure the radiator is full then monitor the overflow bottle. It is true that once you're sure the radiator is full, it will stay that way until the overflow empties.