Hard starting / stalling

Recently my 2001 XJ has been getting difficult to start. It turns over really slow like it doesn’t want to go but eventually will. Today I was stopped at a drive through and it just died on me. It took a min but it started again. I don’t know if it is related but when it is hot in the summer, if I stop the engine for a short time when hot it will start up but will run really rough for a min. It just goes chug, chug, chug… then eventually with a little gas it will get going fine. It was doing that with my old engine and not as bad but still does it with the new one. Does anyone have any ideas what I should start troubleshooting first? Thanks!

The 00-01 XJs are extremely susceptible to "heat soak". Tons of threads on it. There is a TSB from Jeep that I am including for you to read. It is likely your problem with the hot engine. Know that the TSB fix is considered to be kind of lame in a lot of guys opinions. There are other fixes including e-fan timers, louvers, etc. SEARCH and you'll find lots of light reading.

It is possible that you have something else going on though with the "slow cranking". The start to troubleshooting that includes cleaning all battery connections and battery terminals until shiny, load testing the battery, and using a meter at the starter with the key in the ON position to ensure that you are not suffering from "voltage drop" due to a bad cable, bad ground etc.
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TSB (Technical Service Bulletin from Jeep)

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.


TSB for the cold start rough idle and P0303 code: TSB 18-010-01

Agree 100 percent with BirchlakeXJ. Heat soak for one problem, a poor battery, battery cables, starter-solenoid, or some combination of all three for the slow cranking.

Fully charge the battery and have it load tested.

Do a voltage drop test on the cables.

If they both pass consider replacing the starter-solenoid.

Sorry to highjack. But this is close to what my 2000xj is doing. It does not have a rough idle but stalled at a red light and would not start back up. No problem with cranking just would not fire. We thought it was a relay under the hood because once it was replaced it was fine. But it did it again 2 days later just idling in park. I let it sit for a day and started right up. The second stall the motor was not even warm yet. Took it to a friends shop and in 4 days it would not stall for them?

Your issue sounds like thermal failure of the crank sensor.

Next time it dies try pouring water over the crank sensor and then see if it will start.