I just picked up my 2001 sport with 90k and drove it about 100 miles and went to fill up. After the fill up my check engine light came on. I figured it was just the gas cap because it happened with my ex gf's jeep. Light came on and then autozone ran it. I put the cap on tighter and they reset it and it was good.

I figured i'd be going there and get the same code results because the jeep even after the light went on ran fine for 200 more miles home. The test showed

-cylinder 3 misfire
-something relay failure

I started it and it idled a tad rough for a second and then when I got going it was perfectly normal running.

jeep dealer said if it isn't a blinking check engine light it's not serious and to check my plugs and wires. I did so, plugs are fine even cylinder 3. Just drove it another 60 and it ran fine...

What do you think? There's an exhaust leak for sure. It's lifted 3 inches with 31s.

 

The number 3 injector gets hot and vapor locks. What you have to do is put a heat shield around that injector to keep heat from the exhaust manifold causing it to vapor lock. That will fix your problem

 

I was told it was actually a recall maybe I can get it done free

 

cyl # 3 misfire is common on the 99-04 cherokees and grand cherokees.. the design of the INTAKE manifold is POOR.. here is some info on your POSSIBLE problem...

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).