Did you ever resolve this issue? i am having the exact same problem, only once in a while at altitude my 98xj will sputter/stall or when i turn it off will have trouble re-starting. wait 5-15mins and it starts back up and runs fine. i haven't gone and thoroughly checked the sensors but i have replaced (cap/rotor/plugs/cables/ignition coil) i checked the and cleaned the crank shaft sensor it looked fine and it still does it from time to time. any pointers would be great before i go through checking wires and censors. thanks.