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After driving my Cherokee (01' 4.0L) for a while (probably at least 20 miles), I shut the engine off. If I restart the engine before it cools down, I always have a miss on either the #1 or #2 cylinder until I rev the engine up. has anyone encountered this problem??? It is an intermittent problem that does not happen all the time.
 

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After driving my Cherokee (01' 4.0L) for a while (probably at least 20 miles), I shut the engine off. If I restart the engine before it cools down, I always have a miss on either the #1 or #2 cylinder until I rev the engine up. has anyone encountered this problem??? It is an intermittent problem that does not happen all the time.
I have this issue with cyl #3. It's the heat soak misfire that's very common with the newer xj injection systems. There's a number of TSB's out to "possibly" fix it.
 

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This bulletin may be your problem....Cheap and easy fix. I'd start there. I had to perform it on my 01 for symptoms similar to yours. Good Luck!

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.


TSB for the cold start rough idle and P0303 code: TSB 18-010-01
 

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This bulletin may be your problem....Cheap and easy fix. I'd start there. I had to perform it on my 01 for symptoms similar to yours. Good Luck!

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.


TSB for the cold start rough idle and P0303 code: TSB 18-010-01

That's what mine has and still does it.
 

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I did the insulating #3 injector as stated in the TSB... Did nothing to solve my missfire problem.

I saw a thread on JeepForum I think that says it can be caused by a valve in the fuel line that is supposed to prevent fuel from draining back into the fuel tank going bad. If it leaks down you loose fuel pressure in the lines/injector. Try turning the key on and waiting about 15 seconds before cranking it over and see if that does not stop the missfire. It did in mine...that is if I remember to wait before cranking it over.
 

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Discussion Starter #7
My engine popped error codes for a misfire on #1 and #2 cylinders. I'll take some aeroquip sleve and try to insulate in accordance with the bulletin.
 

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Wouldn't hurt to inspect the injectors.
 
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