Audi S5 Starting Issues: Bad Coil vs Ignition System

Had a similar starting issue with my 2010 Audi S4. The symptoms matched exactly, intermittent starting problems and rough running before shutdown. The car ignition system was the root cause, specifically a failing ignition coil pack combined with a defective crank position sensor. The dashboard lights would come on normally with the ignition key turn, but the engine behavior was erratic. Multiple coil pack failures are common on these engines. The crank sensor issue caused the ECU to lose synchronization, leading to the sudden shutdowns. This was a serious issue requiring immediate attention, as it could leave you stranded. The fix involved: Testing all ignition coils, Replacing faulty coil packs, Installing new crank position sensor, Performing ECU diagnostics, Checking fuel pressure Suggest finding a specialist who understands Audi car electronics. A proper diagnosis requires specific diagnostic equipment to read the exact fault codes. The symptoms point strongly to ignition system components rather than fuel delivery issues. Worth checking the fuse box for any blown fuses related to the ignition system before taking it to a shop. But given the age and mileage, professional diagnosis is recommended.

Thanks for sharing those details, sounds exactly like what I went through. The starter motor would crank but the engine just wouldnt fire up properly. Got it fixed a couple months back but cannot remember the exact repair cost. What did you end up paying for the full fix? Also curious if youve had any other ignition key or starting issues since the repair was done? The car has been running great after fixing those coil packs and sensors, but always good to hear long-term experiences from others with similar issues. These starting problems can be tricky to diagnose properly.

Good news, since seeing the mechanic who properly diagnosed the starting issue, my S4 has been running perfectly. The ignition switch problem was fully resolved by replacing a defective fuse that cost 52 Euro, along with the faulty coil packs and crank sensor mentioned earlier. The car electronics are now working as they should, with no more problems turning the key or getting the engine to start reliably. This experience showed how important it is to have a thorough diagnostic process, as a simple blown fuse can cause complex starting problems that mimic ignition coil failures. For over a year now, the starter motor engages instantly and the engine fires up normally every time. Having these ignition system components fixed properly the first time really made the difference in long-term reliability.

Found a specialist Audi mechanic who actually took the time to properly diagnose the issue. Total repair cost came to 780 Euro for replacing two ignition coils, the crank position sensor, and a blown fuse in the ignition system. The car electronics diagnostic test alone was 120 Euro but worth every cent since it pinpointed the exact problems. The ignition key now works perfectly every time, no more struggling with failed starts or rough running. Been about 3 months since the repair and the engine fires up instantly, runs smooth, and stays running. Such a relief after dealing with those unusual shutdowns and starting problems. Really appreciate everyone sharing their similar experiences here. Having a clear idea of the potential issues helped me push for proper diagnosis instead of accepting quick fixes that wouldnt have solved the underlying ignition switch problems.