Odd startup, running rough/missing cylinder

2001 XJ, 4.0 AW4. Warm start-up, turns over/starts but seems like it is missing a cylinder/running real rough. will rev up if I gas it some.

turn it off, restart it and it runs fine, or requires a 2nd/3rd start to run normal?

what could this be? CEL does not illuminate.

TIA, JLS.

EDIT: new spark plugs. could it be the coil pack? causing intermittent issues?

Hmm my 2000 just started doing the same thing. I can shut it down and restart it or let it idle and after about 15 seconds it will smooth out and idle as normal... IDK..

There is a service bulletin that involves insulating the #3 fuel injector if you are experiencing stumbling starts WHEN HOT. Kind of a vapor lock situation. Don't have the specifics at hand; use the SEARCH function or somebody else will chime in. It is a quick/cheap fix if this is it. I also vaguely remember something for your vintage about reprogramming for similar symptoms.

http://naxja.org/forum/showthread.php?t=99985&highlight=insulating+fuel+injector
http://www.naxja.org/forum/showpost.php?p=328304&postcount=4

found a couple links, thanks for the correct search terms.

Now what I didn't see, maybe because it isn't necessary. BUT, the question is. Do I have to remove the injectors for this? I'm thinking not but would like an answer from someone who has done this.

Thanks, Justin

Injectors don't have to be removed to install this bulletin. Here's the procedure:

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