My 02 cummins 2500 4x4 with nv4500 has a rough idle or like a miss after the truck is warmed up. It smooths out if the AC kicks in or you let the clutch out just a little as if you were to roll ahead a bit.  The truck has a new vp44, TPS, and FASS titanium pump. I've seen this problem posted on other forums but nobody had a fix to the rough idle. Anyone have this problem or have a fix for it? Any help would be greatful.

Any codes?

No, at least it would give me a staring point. 

My 02 did that for years, just lived with it as it never really got worse or affected anything else other than being able to hear and feel it once in a while and the weird part was it was only no load hot low idle that it did it same as you turn on the ac or put into gear and it was smooth as silk..Did it through several different injectors pumps and comps/programmers.

I have a little OCD so it drives me crazy knowing that there is something "wrong" with the pick up and I can't figure out how to fix it?

Well, take it out.  And run the heck out of it.  If you cant break it, it must be ok...  its the American way!

 

My 2000 had the same thing but ran beautifully otherwise.  

On 9/26/2016 at 5:30 PM, CSM said:

Any codes?

Just unplugged my comp box to see if it was causing the problem.. Picked up a few codes P0237 already ordered a new sensor from Genos Garage. The other was P0602  control module programming error.

Just unplugging the comp will cause codes and check engine light unless you completely take it out of the circuit and plug the OEM sensor harness back together.

Put a rebuilt head on my truck and it quit idling rough once it warms up. Looks like one of the valves in #1 had a bad seat. Valve sucked up a little. Haven't torn the old head down to check for sure as the truck runs perfect now! 

Thank you for updating and letting us know,  I did hear a rumor that some of these 24 valve heads if worked hard during their life, need a valve and seat job every so often. And some heads crack, it probably has something to do with incorrect warm-up and cool-down, maybe the way it burns fuel also or dirty fuel. My guess if it was a bad seat or a burnt valve, something was keeping the valve from fully closing.

I'm the fourth owner of the pickup so who knows what it's been through. She is almost damn near new now with all the  upgrading and and updates to it. I'm very particular about my stuff so any little hiccup or malfunction I'm looking into it. Hopefully this helps others out. Like I mentioned in my first post, I've seen this problem on a lot of other forums but no definite answer. Thanks everyone for the input.