rough idle on start up

[Pedro]

well yesterday at RC my Jeep would start up and run rough for the first 30 seconds or so. after that it would run fine without a problem. it is not throwing codes or anything. what could it be?

I havnt tried to start it yet today but I will in a little bit when I go out. hopefully it doesnt do it anymore

[XJLI]

probably got dirt/water/mud somewhere. give it a couple days and itll either go away or start throwing codes

[wannabejeep]

mine does the same thing. Although I'm sure its some other issue with mine lol.

[Riot]

Mine has a rough idle all the time, which could be the iac, so I guess im not real help, though i'd like to see how this is resolved. Good luck!

[Pedro]

never mind we all good. I went and drive it today and it started fine. must have had water somewhere it shouldnt or something

[Burton58]

i blame the red hatch

[Pedro]

i blame the red hatch

its sun faded, we went over this

[Adam]

Mine does the same thing. Last summer i noticed it. I had the cooling system flushed. Replaced my water pump, installed a GDI 3 row radiator, new lines and new thermostat. It still does it any time the temp. is over 70*. It'll shake and idle like shit for 30 seconds and then as soon as I put it in gear it stops and the temp drops back down to 210.

[Saharicon]

mine did this when it was over heating at RC the weekend me and will were there... besides that it never does it just when its really hot

[lakailimited06]

mine did this as well when i was at rausch also does it whenever i go wheelin really..

[ninetysix-ex-jay]

Clean the IAC maybe?

[Hydra]

mine does this when it used to overheat

[Pedro]

but it wasnt overheating. it never went past 215

[Krazors001]

Mine does that every few months or so. I'll start it up and it will be bucking between 500-900 rpms and seems like it will stall but the second I step on the gas and drive off it goes away. It does it every few months and has done it for the 5 years I've owned it. At this point, I think the jeep just does it to keep me on my toes.

[OTTE]

If the XJ is a 2000-2001 it might be a Heatsoak issue. My XJ did this and i replaced #3 Injector. There is also a TSB about it.


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