Idle issues a6 c6 2008 2.0

[AAG1989]

Hi all, sorry if my questions was already posted, I have searched through this forum but haven't problem anyone else having a problem like mine, so here it goes.

 

I bought about 1 month ago an 2008 a6 2.0 diesel engine BRE engine code with an automatic transmission CVT, haven't noticed when I bought the car but, my idle RPM when I'm stationary when the engine temp it's at 90 degrades  it's 970 RPM, I did changed the battery with a new one I bought a Varta sylver 110A which I have coded with VCDS , the alternator charging to the front of the car it's 13,80 V and back to the battery 13,45 , battery indicator it's always to 100% even if I listen music for a while. If i'm unplugging the battery ECU from the battery the idle is right, 850 rpm, but i have no charge , I've tried with another battery ECU but no change. I have no error on VCDS.

 

Did anyone else had this type of issue ? ty v much