I just bought a 2004 S4, and although I love the car its not looking good. Driving it home last night the check engine light went on, so this morning I had Audi run a diagnostic on it and several pistons are misfiring. Theyre gonna check it out monday morning but I was looking at the previous owners service records and it looks like one thing after the next. He had it in the shop 3 weeks ago for the same thing, he replaced the tie rods, because it sounded bad when he made sharp turns, and 3 months ago it looks like it wouldnt start and when they opened up the engine they found the alternator belt melted, battery was completely dead, another time the car wouldnt start and they found it was internal corrosion in the starter/clutch relay and they replaced it......... Did I buy a lemon?? Are these problems common?? I

 

No, none of that is normal. Things should not melt, and pistons should not misfire. I would talk to the previous owner, he knows the cars history the best.