Spark plug miss, fuel injector problem, burnt valve, or vacuum leak but the check engine light should be on if this is the case. Also possible broken motor mount if the check engine light is not on.
It is idling. This is hard for an engine to do smoothly.
I think you need a speed sensor
loud, and shety muffler
silent it
Could be time for a tune up.
Hey Ben==Have the engine tuned up and have the motor and trans supports checked. GoodluckJoe
Something is out of balance or the engine mountings are loose....get is checked out.
Low oil pressure = Oil pressure has dropped, STOP Check engine = Problem with the emission's system. Temperture = Engine overheating, STOP Maintence required = Some sort of maintence is due, normally Oil/Filter change.
You have 2 options. Either you put your catalytic converter back on or you unplug the check engine light. Thanks for killing the environment.
The stop engine light might not come on on your N14 Cummins when the switch is off.
Perhaps your timing.
By wearing the seatbelt.