I have an odd problem when the car is warm, in park, and idling. Idle seems to be around 700 rpm but it dips to under 500 rpm and then goes back up. Keeps doing and doesn't stay at 700. Engine idles fine in gear (stopped at light or something), cold start is higher rpms but also consistent. Only happens when the car is warm and in park. Any ideas what could be causing it? No codes.

 

Did you ever find out what it waa