ISX flutters at idle

Just a guess I would say the turbo is sticking or not going full range of movement

 

My 08 would surge, if that's what you mean. It was the EGR sticking. Pete replaced that one. Talked to a Cummins engineer at Louisville[MATS] and he suggested removing the EGR and cleaning it on a regular basis. I did that and had no more trouble. Very simple job and easy!

 

If you have perchance removed The EGR for off road operations, I see what you are saying. If it is still on the truck, I would pull it off and see if it is maybe it is not opening all the way. First time I had about an hour in R&R plus clean up time. It's basically a lawn mower valve with 2 tulips. The spring is pretty weak, I just pushed on it to get the keepers off.

 

A slight amount of air in the fuel will also cause this. Could be sucking in a small bit of air from somewhere.

 

http://www.thetruckersreport.com/tr...3-cummins-isx-cm871-technical-discussion.html

 

I had a surge/fluctuation at cold and then with time hot idle for some time with the truck I sold (in my signature). After chasing this for several years and swapping everything left and right. Including fuel actuators, shutoff solenoid, both fuel pumps and several sensors, I've finally nailed it with swapping "exhaust pressure temperature" sensor. Located on the "hot side" above the turbo towards the front of the block. Though mine was the 05, EGR only (with the "block").

 

Is your turbo actuator is still air controlled or electric? See if they can do a fuelling/timing actuators adjustment. Cummins did that for me once, it helped a bit. But didn't completely removed the idle fluctuations.