Jeep Cherokee 2000 6 cyl. 4x4 miss-firing with hot start

jeep
cherokee

#1

Brooklyn mechanic says “every Jeep Cherokee has this problem–number 3 cylinder mis-fires because it can get too hot”. When I return from the country to the city, unload Jeep at the apartment, then, after about 15 minutes, re-start Jeep, it bucks and rumbles and misfires with no power from motor. I pump the gas pedal, and after about a minute it settles down. I never have this problem in the country. Country mechanic has done smoke tests, looked all over for any compression leak, replaced gas cap, put insulation tape over #3 cylinder, and reported that this problem is in the “data bank” of Cherokee problems, where ever that data bank is. The question is, can one live with this problem, or will it cause more problems? Why does the motor settle down after pumping the gas pedal for about a minute? I’ve had the starter coil replaced recently, as I was told it can get fried from too much mis-firing.


#2

I will have to assume that when this happens the check engine light comes on and if the codes are read that the code “P0303” is read from the computer. Are there any other codes? Does the check engine light flash when this happens?

I have no knowledge of any specific cylinder #3 Jeep issues, but that doesn’t mean anything. I’m just answering on the basis of a generic issue rather than any special Jeep thing.

I will have to assume since a coil was changed that the spark plugs were dealt with very early on and to no effect. And since the coil for #3 has been changed, then I would swap the #3 fuel injector with another one and see if the misfire moves with the injector. The wiring for the #3 injector also needs to be checked.


#3

thanks cigroller. I’ll mention that to the Brooklyn mechanic, where the car is now. The engine light does go on, if I have just had the Jeep worked on and the light turned off. It does not flash, just remains on. The mechanic, when he checks, says something like, “the computer reads mis-fire in the #3 cylinder”.


#4

Have you had the fuel injector insulated per this 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 (from driver?s side of vehicle).


#5

Good score jesmed!


#6

Thanks, cig. Google can make even idiots look smart once in a while. :wink:


#7

Very impressive jesmed. I will try to email that info to car mechanic tomorrow morning. So cool you found this! What phrase did you use on Google for the search?


#8

I think it was “jeep cherokee cylinder 3 misfire.”

Here’s the link where I found that TSB:
http://www.automotiveforums.com/t212532-discuss2000_2001_jeep_cherokee_rough_idle__multiple_cylinder_misfire.html

It’s TSB #1803103


#9

The engines will skip if they develop a crack in the cylinder head. Fortunately on this model you don’t have to remove the head to find out. You just remove the valve cover and look for a coolant stripe in between valve springs near the center of the head. The heads crack right through to the top when they go bad. The coolant stripe like like a grey or brown bulge or ripple that is pretty unmistakable. If you disturb the bulge with a screwdriver you will see coolant.

I have had good luck with reconditioned heads that have been welded. The old repaied heads are more normalized from heat than new heads and they last.