Idle and vibration at 500RPM

[isstatu1]

When I start my car and it idles above 1k rpm it feels smooth. Same while driving. When I'm stopped at a red light the rpms drop to around 500 and I can feel a slight but annoying vibration. As soon as I start moving again it's smooth again. 500 seems a bit low (afaik), where should I start looking?

 

[mguy13sport]

500 is low. Should be around 600+

If you have a scan tool I would check for codes. There could be throwing DTC that don't trigger the CEL.

It could be a vacuum leak or misfire based on the description.

 

[isstatu1]

Scanned with Forscan and took a look at the idle. It bounces anywhere around 580-620. It also sometimes throws a code P04DB crankcase ventilation system disconnected. I clear the code but it returns after a week or two. I'll order new pcv valve as well as tubing.