Why the stumble and rumble at idle??

[Skillet]

Everything is going great, engine purrs like a kitten, new tune up, replaced the injector in #6, etc, etc...
So, I warm the truck up this morning, all is good, drive about two miles down the road, at the first stop light, the engine is stumbling and rumbling at idle. Fluctuating RPMS. I drive about another 1/2 mile and pull over, stumbling and rumbling again. I shut the engine off, let it sit for 30 seconds and start it back up. Runs perfect!
32 miles to work, stop to get coffee, idles perfect.

What the hell was that all about?

No check engine light, or anything like that.

 

[GXO]

did you disconnect the battery during your work? I have seen some madness with idle and mixture as the ECU figures things out after changing things with the battery disconnected.

 

[Skillet]

did you disconnect the battery?

No. About two weeks ago I did, but I have driven it quite a bit since then.

 

[NorCalDoug]

I picked up the same symptom a couple weeks ago after coming off the trail...I haven't pinned mine down yet.

 

[sseaman]

check your vaccum lines there is one i knocked slightly loose changing my pcv and it would not idle for long, this is all that was missing, good luck