Hi Kimohands. Sorry for reviving an old thread but was wondering if you managed to sort this problem out?
I’m in the UK and have exactly the same problem. No fault codes, no spanner light and my car drives fine though reversing up a hill is a nightmare.
Did you find that the fluctuating also depended on engine temperature? With mine the difference between high and low fluctuations decreases as my engine warms up and the idle speed increases to about 1K rpm. Then when the rad fan comes on the idle reverts back to 950 high and 650 low roughly two seconds for each. As the engine gets hotter it starts all over again.
Thanks
Dave