500rpm idle in drive

[Torque Splitter]

So this started happening about 2 years ago and the problem hasn't gotten worse or better. In drive the vehicle idles at about 500rpm at a stop. I've tried to adjust the idle screw located at the throttle body with no luck. if i move it up the drive idle will move to about 750rpm in drive but in park will fly up to 1000-1200. It never dies and the IAC is working properly at this time. the only long term problem im aware of it premature mechanical wear due to low oil pressure at 500rpm. Does anyone have the same issue?

someone else also suggested that the torque converter could be prematurely locking up creating an extra load on the motor. I've since dismissed this because it will almost always stall the motor

[ARK]

Did you clean your IAC and EGR ? Also your intake at the TB could be carbon fouled. A can of carb cleaner sprayed into the throttle body can do wonders or even Seafoam but use it sparingly. If you clean your throttle body do it just before you change oil, then get rid of that oil and put new in.