I started noticing a little bit of a shudder in my idle after I ran out of gas one day a few months ago. Lol. I know. A totally different issue there. The idle before used to be considerably smooth with just an occasional noticeable blip. But nothing consistent. I have since ran fuel injector cleaner, changed all the spark plugs, put all new intake manifold gaskets in it, and a new tensioner and idler pulley. It also has a new serpentine belt. The issue has not really changed. I also took the tune off of it and re-loaded it to make sure everything was reset. The car runs fine and the performance has not been affected at all. It’s only when you sit and idle that you notice it. I would think if it was an injector or a coil pack or some thing with a cylinder it would be throwing a code. My only other thoughts would be could a water pump or another pulley having issues cause this sensation? Or possibly a fuel pump issue? Just looking for brainstorming ideas to troubleshoot this. Thanks.
Also, what kind of fuel injector cleaner did you use? They are all not equal; the ones with PEA are best for the type of carbon deposits that can build up on the backside of intake valves and cause things like poor idle and lower fuel economy.
Start looking for Top-Tier stickers on the gas pumps you use as well. The Top-Tier fuel has a smidge of PEA in it already, thus mitigating the need to run a separate fuel system cleaner periodically.
Amsoil fuel injector cleaner and Costco Top Tier gas which I was told by my tuner was really good based on my logs I sent him. Plus when I did the intake mani gaskets I used Amsoil PowerFoam and cleaned out all of the head ports real well.
When you ran out of gas, the fuel pump may have picked up some debris from the gas tank. Is there a pre-fuel filter for the electric fuel filter on our Challengers? If so, I'd change that.