99 century cummins n14 chugs a lil now and then. Radiator fan comes on stays on.

Have you tried turning the fan by hand,when you turn truck off,do you here air exhaust from fan?

 

It could be a bad Injector or pass-thru wire to the Injector. I had the same issue with my N14 a few months ago, except it was only at idle though, no codes either.

The Mechanic changed the Injector and found a bad connector on the injector harness next to the cylinder head. He said it might be a flat lobe on the camshaft, but I don't think so because no loss of power and it misses only at idle.

I also changed the Camshaft Position Sensor since I read that it will sometimes get debris on the magnet that can cause issues. It's only $35, and it's a cheap fix.

We also swapped ECM's and no change what so ever.

It runs smooth now, but once in awhile it seems like it still has a barely slight miss at idle, but it does eventually go away.

 

No Check Engine light, I just changed it because it was the original one and I read you should change it at 500k miles regardless, and it was a cheap part anyways, so it couldn't hurt.

 

Try injector maybe or could be wiring my grandpa told me he has a 99 century class with a n14