My idle softly goes up and down from around 5 or 600 to just below 1k.

Guesses or similar experiences??

d series all stock

 

Simple fix, there's a brass set screw on the top side of the throttle body where the intake connects. Just screw it in a tiny bit at a time with the car idling and it should stop.

 

I would clean the throttle body first, then if that does not fix the issue, check for vacuum leak.

 

Trying to clean the throttle body will have no affect.. my car has had this issue along with 2 friends.. it is a easy fix with just a slight adjustment of the screw. My buddy had to turn his in a full turn while mine was half a turn and also idle rpm stayed at 750..