00cherokee00

Just looking for some opinions before I start working on my 2000 cherokee.
Got a cylinder 3 misfire code. Jeep runs great when started cold and drives fine until you shut it off. Say going into a store for 30 minutes and coming back out. Then when trying to start, the jeep has a strong misfire and you have to race the motor to get it to clear up. Any opinions are apreciated.

2000 Jeep Cherokee Sport 4x4
4.0 L6 Automatic

skarpenz

Plugs, wires, cap, and rotor are a great place to start, and should clear it up fine. Try it out.

00cherokee00

2000 model cherokees have a direct ignition system which means no cap, rotor, or wires. The coils sit right on top of the spark plugs which only have about 10k miles on them. I would like to take a multimeter to the coil packs but it is all one unit with a wiring harness attached to one end. I need a wiring diagram to know which connections on the harness are for the #3 coil. Anyone have any ideas where I can find a labeled wiring diagram for the coils?

XJ Stryker

I hate to tell you this but if you run a search on NAXJA.org. There are alot of technical writes up there. This site is great but not as much info YET.

skarpenz

Oh man, I didn't even realise that the 97+ was COP ignition. It still has plugs though, and plugs can go bad no matter how many miles. If you need diagrams, pick up a Haynes manual. It will also help you troubleshoot.

Kyle

00+ Has a coil pack.

BlueXJ

It also may be the connection to the injector for number 3 cylinder. When you rev it enough then the bad connection is overcome by the signal from the 'puter. Check that you have a tight connection at the injector. See if it makes a difference.
What exactly does the code read?

00cherokee00

p0303 is the code. It reads "cylinder 3 misfire".

rockinxj00

i would check the coil pack as well. if thats it, you may want to try to find one on e-bay or something cuz they are pricey.

jeeptech

Not a plug or coil problem, this is a fuel problem - #3 fuel injector is probably leaking and fouling plug in #3. This is something I have repaired several times. It is easy to confirm. Start it up for a few and shut it down. Now take out the fuel rail an watch for #3 to drip. Do not disconnect fuel line as you may need to repressurize the line to see the leak. Replace any/all leaking injectors and a fresh set of plugs after the fix won't hurt.

heymrg01

I spent way too much time any money chasing this very same problem (#3 misfire) on a 2000 XJ. Plugs didn’t fix it. Had the coil pack replaced to fix the misfire and the light stayed off for a week +/- only to come on again. This time the code was catalytic converter related. It was explained to me that since I ran the thing for so long with the misfire condition it was spitting unused fuel into the exhaust system, damaging components there. Before replacing a converter, we did the pre and post sensors to it and the light has stayed off so far. If it comes back for the same code the converter may be next. Goes to show how leaving one problem go for too long may cause a more costly chain of events... I am not convinced this issue is over as it’s been “nickel and diming” me for over 6 months. Good luck. One thing I’ve learned from this forum is that this code seems to be a common one so anyone who has experience with this – PLEASE REPLY with your fix – for ALL of us! Hope this helps.

moses

Just how many miles are on these 2000 jeeps? Previous;y had you run any fuel additives ( sea foam, gum out Etc) ?

muddeprived

I had the code twice on my 2001 xj since i bought it last year. I haven't cured it yet, just erased the code. I get the p0303 code after driving it for extended periods of time. After i shut it off and restart it, it will throw the code and misfire. Some say it's vapor in the injectors or something like that. I'm not too worried about it since mine doesn't happen that often.

SeriousOffroad

1803103 - 4.0L ROUGH ENGINE IDLE AFTER RESTART FOLLOWING A HOT SOAK
Date: 09/05/03 (supersedes 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 (from driver’s side of vehicle

RicanXJ

Good info