So I have a 99 1500 318 5 speed I purchased recently. It was not running and has not for roughly 4 years due to a crank sensor so I replaced it with a standard ignition sensor. Upon getting it running it had a odd misfire at a idle but if held at a certain rpm there was no issues and occasionally on start up it will through code p1391 for intermenant signal loss on cam and crank sensor and cuts the motor out majorly in 5th gear until i clear the code. so I replaced cap, rotor, plugs, wires and fresh fuel with no luck. I'm just at a loss

 

Timing chain slop maybe, and check plenum

 

If you replaced the crank sensor and you are still getting the code(assuming you cleared it) It's probably an issue with it. Replace it with a mopar or delphi brand sensor and stay away from whatever the local parts store sells.

 

See I was think that but I don't get the code every time it's just occasional on start up. I would think if the sensor was bad it would throw it none stop.

 

I had the same type of intermittent issue with my crank sensor. It was an aftermarket BWD sensor. Sometimes, the engine would just shut down. I could come back about 20 minutes later and the engine would start up fine. One day, I was heading down the road and the engine just cut off. I drifted off the road and connected my scanner. Up came pending code P1391. I disconnected the battery cables and re-connected them and the truck started back up again. I was able to make it home and immediately ordered a new Mopar crank sensor from a dealer via eBay. I've installed the new Mopar crank sensor, cleared the code and had no more issues.

 

If it's only at start up then it could be the cam sensor. After the engine starts the cam sensor is not used.

 

​​​​​​​BWD = Broken When Delivered

 

Maybe something, maybe not.
I had "the mystery die" on my beast. '96 Ram1500/5.2/250K miles. The engine would 'mystery die' on an inconsistent/periodic basis. No regularity, no codes, no apparent cause. It would just die...N THEN miracle of miracles, t'would come back to life. There's the WTF, now for the What To Fix?!? I got a bi-directional scanner a couple'o years back, n set my fuel sync (19 degrees off). Not 1 more 'mystery death' since. I understand that not everyone has $700-800 bucks burnin' a hole in their pocket, I damn sure didn't, but it worked for me.

 

A vintage Snap-On MT2500 scanner, appropriate cartridge and personality key can perform a '94-'01 Dodge 5.2/5.9 magnum fuel sync function. They can be found used in all kinds of places, usually fairly reasonably, such as Craigslist, eBay, Facebook Marketplace, etc. If you plan to keep the truck awhile, they are handy to have on hand.

 

The sensor did work for about 3 years before it went began to intermittently fail. I know now to get the Mopar sensor for critical functions, such as this.