paul3654

Hello , I have a 2011 A5 2.0t awd and the issue i am having is every morning it has a rough idle or misfire at startup only when its at high idle 1800-2000 rpm then it smooths out when it drops down to normal idle it only happens when the car sits for a long time , I've changed the crankcase breather ( pcv valve ) plugs , throttle body , coils i'm thinking maybe one injector is leaking and flooding it out ,other than that the car runs great

My Audi MPS

Had the exact same issue with my S5. Turned out to be stale fuel.

S4'ed

Perhaps excessive carbon deposits on the intake valves and/or runner flaps.

Or leaking injector.

Or a head gasket failure.....when the car sits overnight, after a hot shutdown, a little bit of coolant leaks into one of the cylinders (the coolant remains under pressure until it cools down), and when you start it up the next morning, there is a spark-miss on that cylinder until the coolant is expelled. Other than slowly losing coolant, and the cold start misfire, the car ran fine after the cold-start misfire cleared.

After it sits overnight, and is cool, remove all the sparkplugs, and use a flashlight to look at each piston-top. If one appears wet/shiney, you have a bad head gasket.