Does it do it when cold starts? Or only after running?
http://www.jeepforum.com/forum/f9/cleaning-iac-throttle-body-write-up-dummies-1114849/
Also check for leaks around the TB, injectors and intake. Somtimes they are small enough leaks they close from the engine heating.
Failing O2 sensor-you could unplug the sensor to see if the condition goes away. You will get a CEL and I don't recommend running like this, only for trouble shooting.
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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.
18-031-03 -2-
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
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http://www.jeepforum.com/forum/f9/cleaning-iac-throttle-body-write-up-dummies-1114849/
