I've been having issues over the last month with my 99 with a 4.0. I keep getting codes P1391 and
P0340. I've replaced the crank sensor four times and the cam sensor once. I'm convinced it's not a sensor issue but I can't figure it out. It will randomly not start. Then I'll go out to it and it'll fire right up and run for days. Help!

Check the wiring going to cam sensor.

How far back should I chase those wires?

Go to the firewall. Make sure heat from engine didn't cause any breaks or cracks. That was my issue.

Was it pretty intermittent?

Very. I chased it for 2 months.

Ok. Thanks. I'm gonna check it out

What kind of sensors are you using? Mopar, Autozone, Napa, ect? Just curious because everything that I have read on this forum says to replace sensors with Mopar, because the 4.0 is really picky. I'm no expert by any means, it's just what I've read on here. Good luck!

The last two were from the dealership

Oh man, sorry for the bad luck. I'm sure someone on here will know the answer to your problem. I definitely want to know.

So I spent a couple hours following wires from both the crank and cam sensors. Didn't see any parts where bare wire was exposed. The wires were a little roughed up and pinched in a couple spots but no breaks or anything. I ran them in a new and separate piece of loom. I also checked that the cam sensor and wheel were good and they are. Finally I disconnected the battery for a while just to make sure the computer got a good reset. We'll see how it does when I leave for work in the morning.

Is this dist or coil pack ? Maybe dist bad causing excess play ?

It has a distributor. I checked play when I had the cap off. There pretty much wasn't any.