raggion19

My 2001 Cherokee 4.0L with 116,000 just threw a code saying cylinder 1 and 3 misfire. It was vibrating badly the other day when I started it with little if any throttle response. After a few times turning it off and on, it was fine. I was wondering if my coil pack could be going? I am running Bosch Platinum 4 right now and I also read that the 4.0 doesn't particularly like platinum or Bosch plugs? Any help would be appreciated.

Jeeptunes

could be coil i was gonna say change the plugs but when u said about knowing the model plug i knew they hadnt been on that long lol and i know for a fact that motor is good for 400,000 miles. check and make sure all wires are pluged in all they way on plugs and coils

raggion19

My friend and I had just pulled the coil pack today and nothing really appears to be wrong with it. Of course I have no way of actually checking if it's good or not. The plugs however appeared to already be worn down and they've been on for three to four months at most. either way, I wouldn't recommend them and will probably switch them out soon.

MarkJRust

Is this after a heat soak?

There is a tsb for misfiring on our model year ('01) after heat soak and starting the engine again soon after. The fix is a insulator/cover (for lack of a better word) over the injectors. Specifically #3 for me.

Jeeptunes

what is a heat soak and can u define tsb as well im having a brain fart

MarkJRust

Heat soak would be driving it around for awhile with the engine at operating temperature.

https://docs.google.com/viewer?url=h...wj_1803103.pdf

This bulletin is supplied as technical information only and is not an authorization for repair.

THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 18-027-02,
DATED SEPTEMBER 06, 2002, WHICH SHOULD BE REMOVED FROM
YOUR FILES. THIS IS A COMPLETE REVISION AND NO ASTERISKS
HAVE BEEN USED TO HIGHLIGHT REVISIONS.

SUBJECT:
4.0L Rough Engine Idle After Restart Following A Hot Soak

OVERVIEW:
This bulletin involves the installation of a fuel injector insulator sleeve.

MODELS:
2000-2004 (TJ) Wrangler (Domestic and International Markets)
1999-2004 (WJ) Grand Cherokee (Domestic and International Markets)
2001-2004 (WG) Grand Cherokee (International Market)
2000-2001 (XJ) Jeep Cherokee (Domestic and International Markets)
NOTE: This bulletin applies to vehicles equipped with a 4.0L engine (sales code = ERH)

SYMPTOM/CONDITION:
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.

DIAGNOSIS:
1. 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:
Qty. Part No. Description

1 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.
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 (from driver’s side of vehicle).

POLICY:
Reimbursable within the provisions of the warranty.
TIME ALLOWANCE: 0.2hrs

FAILURE CODE:
AM Authorized Modification

raggion19

Just an update (overdue but nonetheless). I replaced the plugs with the cheapest champions I could find. Haven't had a problem yet. The Bosch platinum 4s were completely shot just after about 3 or 4 months. I haven't had much time to look into the coil pack because my water pump and electric fan on higher up on the list right now. I could still need a coil pack but we'll just have to wait and see.

salad

For 2001 the NGKs coppers are OEM. They switched from Champion in 2000 as they NGKs seem to hold up better with the coilpack ignition (fires a waste spark)

Rere1992

My 2001 does the same thing. It's most likely heat soak like everyone else said.

kmac25

I am having a similar problem, i have a new coil pack but i can't get the wiring harness off. Any suggestions would be greatly appreciated. I have already added a insulator sleve and cps.

offroadordnance

Did you pull the plastic locking tab out of the coil connector? Otherwise, with it out, you press down on the release tab and pull off the connector.

kmac25

yes i got it off, it was just being stubborn, but the new coil is on and it seems better, time will tell. Thanks for the info!

IonlyBuyJeep

With the new coil pack did you notice any improvement in engine performance and/or gas mileage?

IonlyBuyJeep

It's interesting that you guys are saying copper is better than platinum for this year cheroker. I've used copper and platinum plugs in my 2000 Cherokee 4.0L and I find I get better engine performance with the platinum plugs.