My 2000 cherokee has a blinking check engine light. I get a reacurring check engine light for my jeep for a cylinder 3 misfire (which I have gotten the cylinders fixed twice and the coil pack fixed once) I just drove the truck from New York to florida and the light came back on when I arrived to florida. I had the jeep fixed before I left New York but now the lights blinking which it has never done before. I called my mechanic to look at it tomorrow but I would like to prepare myself before he tells me what it is/can be. Any help would be greatly appreciated!!!

 

Does the light always blink or does it sometimes go off or stay solid? Does it run rough at all? It sounds like heatsoak might be causing that misfire code.

Here's some reading for ya:

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 theexhaust*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.

 

The engine light that I always get for this is always solid. When I start it for the first time during the day it'll start fine. But after that it will rough start and eventually idle normally. Some days it won't even do it. The engine light is always read as a cylinder 3 misfire. I've had this fixed twice and the lights never blinked before until today and it also gives off a scent of burnt rubber.

 

That sounds like heat soaked injectors..read this info..

https://www.cherokeeforum.com/f2/eng...issues-128947/

https://www.cherokeeforum.com/f2/200...o-i-fix-59457/

 

Thank you for the help!

 

Agreed with Dumajones. The blinking CEL means the engine is (currently) misfiring severely enough to damage the cat.

 

Check the head for a crack around the #3-#4 area.

 

Did the level of coolant drop in the reservoir bottle after your long trip? If it did, you'll need to read up on 0331 cylinder head cracks. How many miles on the heep?

 

It has 160k. I was told today that the injectors are fine and its possible the coil pack might be defected. Was also told If this doesn't work then it could be the computer. Grr

 

Not to contradict your mechanic, but try insulating #3 injector before you spend more money. See Dumajone's link. It's a common problem.
Also look at the coil pack where #3 plug seats. Arc marks? Carbon tracks? Cracks in the plastic? That's often what you find with a single cylinder misfire.
If the pack itself is bad you should have two cylinders misfiring, they fire in pairs.

 

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).