You go to a mechanic!
depend serveral things , you have to tell more of the problem
plugged cat, but make sure you check your spark plugs and wires. If its time to change them , then change them first and drive the car. , if sputtering continues, check the cat and the ignition coil.
i would check out the injector pump. it is a common problem with that model cummings.
Sounds like a blown head gasket or a cracked head. does the car overheat? check for water in the oil, or oil in the radiator.
Have vehicle scanned to determine problem
Usually a sputtering muffler means that a new catalytic converter is needed. The sputtering sound is the car misfiring.
Have vehicle scanned to determine the problem-- Could be 1 cylinder not firing due to bad ignition coil or more serious problem
check distributer i had the same problem oil got into the distributer and messed it up whenever i went to a like 3 rpm then the car wouldn't run after sputtering for awhile
== == Fuel starvation. Check fuel filter for clogs, and check air filter for excessive dirt. Also need to check ignition timing and spark plug condition. In other words do a tune up on it.
If a car is sputtering at high RPMs, the fuel pressure needs to be checked. If the fuel pump can't keep up, this will cause sputtering. Also, the car should be checked to make sure the valves are adjusted properly.
It needs a tune up.
What kind of car?