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Old 04-08-2010, 08:45 AM
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WJ Hard start when hot

Friend of mine has a 1999 WJ 4.0 runs great but if you shut it down after its hot and try and restart it, it chugs and has a hard start. If he shuts it down for 15 mins and start it back up its smooth again. Any ideas? 135k mile new plugs k&n intake.
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Old 04-08-2010, 08:57 AM
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Re: WJ Hard start when hot

try runing some seafoam threw her. it may also be a air intake temp sensor happened on a friends car. not sure if the 4.0 has one but worth a shot.
try the seamfoam trick with the intake and in the gas.
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Old 04-08-2010, 03:41 PM
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Re: WJ Hard start when hot

There is a known issue with the "newer" 4.0L engines that involves the heat soaked engine causing the fuel in one of the injectors to vaporize and giving what amts to a misfire if you attempt to start the Jeep before it cools down. Strange thing is, it can pop up at any time even if it never happened before. There is a TSB on the issue and a kit you can by from mopar to shield the injector. I did it on my wife 01' WJ and it took care of the issue for me.

I'll go see if I can find the TSB or the part number of the kit. If I do, I'll post it up.
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Old 04-08-2010, 03:57 PM
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Re: WJ Hard start when hot

Here ya go!

Quote:
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 (90F) 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.
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Old 04-08-2010, 06:25 PM
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Re: WJ Hard start when hot

I have a very similar problem... Thanks for the info!
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Old 05-01-2010, 06:48 PM
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Re: WJ Hard start when hot

I know its been a while but im not on here very often. I passed the info on to him ill let you guys know the result. I found out he used bosch platinum plugs when he did his tune up. I told him thats a big no no im not sure if he replaced them with elcheapos yet. Thanks guys!
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Old 08-22-2010, 06:21 AM
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Re: WJ Hard start when hot

Please forgive my ignorance, but why are the Bosch Platinums a no no?
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Old 08-22-2010, 11:19 PM
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Re: WJ Hard start when hot

You should never use a platinum plug in anything that didnt come with a platinum plug from the factory. The 4.0 loves cheap plugs. Champion is what came in them from the factory autolite works well also. Cheap standard plugs are the way to go.
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