Sorry for posting in the a4 section (i have an a6) but from experience people are on this section more than the a6 section and my engine is technically the s4 engine.
So, i have an a6 2.7t and over the last couple of months its been taking longer and longer to start, so much that in knackered my battery (now replaced). When the car is warm, it will fire strait up. Some days it will fire after 10-15 cranks (thats a good day) but even then, you have to keep your foot down untill the revs pick up, on the other hand if it just about starts and i take my foot off the pedal and it sometimes conks back out, if it does do this i have to leave it half an hour as it just wont start! Sometimes it can take 100+ cranks to fire up (maybe more as i cant count that quick) during this you can hear and feel the car trying to fire and smell alot of petrol coming out the back.
So, any ideas???? fuel pump? coil packs? 02 sensors? ? ? ? ? ? ? ? ? ? ? ?