Idle speed fluctuates

[Dimler]

My 2014 Ram 3500, 6.7 diesel, 68RFE, 4x4, starts fine and idles at a constant rpm. When I drive it and stop, like at a Stop sign, the idle speed fluctuates from 700 to 750 rpm. Selecting neutral or park stops the fluctuations. Anyone have some idea what is causing this?

 

[Hoefler]

A/C cycling will cause this

 

[Topzide]

I've seen this on mine and as @Hoefler, has stated, it's when having the A/C or defrost on. It caught me off guard the first time it happened. Just one of the hiccups in our trucks! As long as your are paying attention to your truck, you'll know when something is really off! The DW thinks I'm nuts in how I play attention to how vehicles sound when driving at different speeds. Gives some insight in how well things are. She just gets in and drives and I only get the heads up when it's too late! I have to fight hard to get her to watch gauges, listen and feel how her SUV handles when driving! We know when something doesn't feel correct with our trucks. Drive on and enjoy them!

 

[Dimler]

I've seen this on mine and as @Hoefler, has stated, it's when having the A/C or defrost on. It caught me off guard the first time it happened. Just one of the hiccups in our trucks! As long as your are paying attention to your truck, you'll know when something is really off! The DW thinks I'm nuts in how I play attention to how vehicles sound when driving at different speeds. Gives some insight in how well things are. She just gets in and drives and I only get the heads up when it's too late! I have to fight hard to get her to watch gauges, listen and feel how her SUV handles when driving! We know when something doesn't feel correct with our trucks. Drive on and enjoy them!

Thank you for your reply, but nothing changed when I turned both the ac and the defroster off.

 

[Ozymandias]

Leave it alone, it will give you a code if something is wrong.
You are hunting a ghost right now as idle speed is controlled electronically and involves a bazillion of parameters.