Two problems related to engine failure have been reported for the 2004 Audi S4. The most recently reported issues are listed below.
2004 Audi S4. Consumer states vehicle failed while driving, engine, power brakes and steering locked up the dealer informed the consumer, the vehicle had suffered catastrophic engine failure, which was most likely due to the failure of the timing chain or adjusters. The consumer was quoted a price of $24,000 for the repairs. The consumer has since learned it was a relatively common problem for his model and year. The specific mechanical flaw seemed to be that the timing chain coordinated the action between the pistons and the valves. The timing chain was supported by several plastic guides. The guides pushed against the chain by the adjusters.
Engine failure going 45mph due to broken valve spring. Faulty part documented in 5/2005 USA today but Audi will not repair.