I am from seatcupra.net and have a 57 plate Cupra which is near identical to the S3 engine , reason i am posting here is my car suffers from missfiring at idle and when out on the road.
I have searched through the various VAG forums to see if i could find an answer to this and also see if other people have the same problem.
Well my car is bogo standard no mods at all , my problem first started at 4,000 miles , and has had exhaust changed , cat twice , new coil packs , plugs and new maf sensor all of which failed to fix the problem.(no injectors yet)
My car is now on 11,000 miles and has been at my dealership for the last week and i have recieved an update which i thought i would share , hopefully will give u guys another avenue to try with your dealers.
Basicaly they have found that cylinder No 3 has a very high compression ratio compared to the others , i have asked what would cause this and at the moment all they can tell me is a valve issue , the head is coming off this week and they will know more once its off.
I dont think that this is a coincidence to the problems that your S3 drivers are having ? thought i read some posts about injectors on Cylinder No3 being changed?
Any way thought i would let you guys know that its not just the S3 which is suffering this problem i also know of a lot of Edition 30 missfire issues as well.
I will post back with any updates that i have.