ArtRS

Hi All, please forgive if I have posted this in the wrong place.

I have a 2014 RS7 which a few weeks back had the engine light flashing on the motorway all of a sudden, drove home fairly normally but when putting into reverse started trying to bounce back onto the drive, recovery came out,started it and revved it and all fine, no warning lights, drove to town normally and smoothly and then same happens again,

had a mechanic come out and it seems quite some time ago 2 spark plugs broke their ground arm as the break was soot black. Spark plugs replaced and engine running and revving smoothly up to 30mph then light comes on again and the hopping back onto the drive starts again.

does anyone have any ideas what this could be?

tia