My e46 idling issue

Good day fellow fanatics, My E46 318i started idling very strange when the car is on normal temperature. It will pick up to 1600 revs, then drop to 1000 revs. Pick up again, drop again. This will happen the whole time. I have googled this and found 1 exact similar thread but the page doesn't open up. Have anyone encountered this and how did you fix this?
Thanks, Petrie