O2 freightliner columbia rough idle

Literally a hundred different things. Start with the simple stuff. Start it up and open the hood. When it starts stuttering start wiggling wires from the ecm.

 

I'm not saying that's what it is for certain, but it cost nothing to eliminate. It's a 15 year engine, if anything like my 15 year old detroit, the harness is starting to work loose at all the connections.

 

Id start with replacing the fuel filters 1st,before I bring it to the shop,youd be surprised what's in the fuel,my truck did the exact same thing and it was the filters,not saying it's da same with yours,but it's cheap and it's the 1st thing I'd start with,hope it helps,btw I have a 60 series 12.7 Class of 99

 

Don't spam please Sir. You can always edit and it will look better.

Fuel filter is my go to idea. I bet you aint replaced them in a while. I ran a Century 2001 in a husband wife team situation with FFE. 221000 miles on it too in 9 months.