Low idle
 

Hi all . I have the following problem: for the last couple of months my engine 2.0t is running at idle with lower revs than the normal. When I use my scan tool it says 660rpm (+ - 5 ) which does not sound normal. I don't mind it running with 660rpm but the engine vibrate and I feel it on the steering wheel . When I try to rev the engine something like a misfire just appear for second and then everything is fine. When I press the accelerator and make it revving at 750rpm (the best idle speed for me) the engine running so smooth that I can not feel and hear anything inside the car and from this point when I rev it there is no any sign of misfiring . What do you think can cause the engine to run with so low idle?
Thank you .

I'm having a similar problem on my s80 2.0t which I've posted here.

Maybe a solution to one will also apply to the other.