This info was on Jeepsunlimited some time ago, I was having the heat soak problem which local jeep dealers seemed unaware of the problem.
You would think servce bulletins would be circulated world wide.
It is still only a partial fix does not completely eradicate the issue. Switching to premium fuel seems to help also.
1801301 - ROUGH IDLE AT COLD TEMPERATURES
Date: 06/11/01
Model Year(s): 2000
Description: Some vehicle engines may exhibit a rough idle and / or Malfunction Indicator Lamp (MIL) light on condition upon initial start-up after a cold soak when temperatures are below 50 degrees F (10 degrees c). This bulletin involves selectively erasing and reprogramming the Powertrain Control Module (PCM) with new software (Cal level 00Cal15C).
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1801001 - ROUGH IDLE AT COLD TEMPERATURES
Date: 04/20/01
Model year(s): 2001
Description:THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L (ERH) ENGINE BUILT PRIOR TO APRIL 30, 2001 AND CALIBRATION LEVEL PRIOR TO (LESS OR LOWER THAN) THOSE LISTED IN THE OVERVIEW ABOVE. This bulletin involves selectively erasing and reprogramming the Powertrain Control Module (PCM) with new software (WJ/TJ — calibration level 01Cal14C, XJ — calibration level 15B.)
Details: Some vehicle engines may exhibit a rough idle and/or MIL light “on” condition upon initial start-up after a cold soak when temperatures are below 50°F (10°C).
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Some may experience a multiple misfire, here is the tsb for that:
0900303 - 4.0L MULTIPLE CYLINDER MISFIRE
Date: 08/01/03
Model Year(s): 1999-2004
Description: NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 4.0L ENGINE. This bulletin involves inspection of all engine exhaust valves and a decarbonizing procedure if necessary.
Details: The customer may experience an incident of engine misfire during certain vehicle operating conditions. The misfire may occur when the vehicle is operated between 50 - 70 MPH and under light loading conditions, e.g. slight uphill road grades. This condition may occur at all ambient conditions, but is more noticeable when ambient conditions are less than 0 C (32 F).
If the vehicle is equipped with On-Board Diagnostic (OBD), a MIL illumination may also have occurred due to Diagnostic Trouble Code (DTC) P0300 - Multiple Cylinder Misfire. Various single cylinder misfire DTC’s may also be present. If the frequency of misfire is high the Powertrain Control Module (PCM) may place the engine in “Limp-In” mode.
The misfire condition may be caused by one or more engine exhaust valves that are slow to close. Late closure of an exhaust valve may be the result of no valve rotation and associated build up of carbon on the exhaust valve stem.
This condition may occur when the engine is not allowed to run at engine RPM’s that are greater than 3,200 RPM. At 3,200 RPM or higher the engine exhaust valves will rotate if not impeded by high carbon deposits. Low engine RPM’s and high carbon deposits are associated with short trip driving where the vehicle engine is not allowed to fully warm to normal engine operating temperatures. Cold ambient temperatures will increase engine warm-up time and add to the opportunity of carbon deposit build-up on the stem of the engine exhaust valve.
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another:
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 (from driver’s side of vehicle).
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