Check the throttle body cables and hoses on the plenum. Make sure its clean and fully pulls back to a tight cable if not you can adjust by turning the black screw adjuster thingy that's on the cable.

 

I keep a ScanTool OBDLink LX Bluetooth & an old Samsung Galaxy S6 in my console with the GEMS ECU Utility app installed on it. I could never get it to work on my S8.
Once every few months my idle will go wacky for a day or three. Don't know why. Don't rightly care.