It's the crank sensor!
Join Date: Nov 2007
Location: Central Minnesota
P1391 is intermittent loss of the "crankshaft position sensor" signal OR the "camshaft position sensor" signal.
As you have replaced the crank sensor and it hasn't resolved, time for a new cam sensor.
Good luck and keep us updated!
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!