RE: 2003 Jeep Grand Cherokee stall problem
It sounds to me that it may be a matter of the Computer relearning the Idle Speed. Drop in a fully charged battery and see how you go.
A car battery will discharge while the iginition is off due to some aof the Accessories drawing a small amount of current for the Clock, Radio, Computer Memory and others.
A Car Battery will also self discharge over a period of time.
Car batteries need to be maintained in a fully charged state. It's not a good idea to let a car battery sit for 3 months as the Sulphuric Acid will cause Sulphation of the plates. You'll have trouble then of the battery holding and maintaining a charge.
Try and hook up a battery Charger to the battery and see if you can get it to charge up. Sometimes you can be lucky and you won't have a problem.
If you ever have to leave the vehicle again for a month or more, it's probably a good idea to disconnect the battery by removing the earth terminal on the vehicles battery. Fully charge the battery before going away and when you get back, pop it on the charger till it's fully charged and you should have minimum trouble..
Anyhow, let me know how you get on.