Is it throwing any codes? Check engine light on? Did you cycle key to see if any codes are stored, even if there is no check engine light.
Sounds like you experiencing similar issues to me. Most people are telling me to look into the timing, and see if the chain jumped a tooth. I have a 4.0L so it is different than you, but it might be worth looking into obviously.
I also had a Grand Cherokee which had similar issues. It was an automatic, and it would lose power, run rough, and eventually die. Did it to me on the highway at one point. I swapped out the Throttle Positioning Sensor, and drove it 1500 miles home with no issues. Might be worth your time to swing by an Autozone, purchase the sensor, and return it if it doesn't help.