RS5 Rough Idle & Stalling Points to Failing Coil Pack

As someone with some hands-on experience working on Audis, I had a very similar issue with my 2016 RS4. The symptoms you describe match exactly what I experienced, rough idle, engine hesitation, and check engine light coming on. After taking it to my workshop, they diagnosed a faulty connection in the ignition system. One of the coil pack cables had become loose and was making intermittent contact. The spark plugs were firing inconsistently, causing the engine hesitation and rough running. The total repair cost was 95 Euro, which covered diagnostic time and fixing the cable connection. It was a relatively simple fix once properly diagnosed. The repair resolved all symptoms immediately, smooth idle returned and the check engine light cleared. Before suggesting anything specific though, could you share: Current mileage on your RS5, When was your last spark plug change, Are you getting any specific error codes, Did this start suddenly or develop gradually This information would help determine if your issue is identical to what I experienced or if there might be other factors at play with the ignition system.

Last service was at 165000 KM and I am now at 170384 KM. Vehicle diagnostics showed error code P0301, suggesting cylinder 1 misfire. The issue started gradually over the past few weeks. Regarding spark plugs, they were actually changed during that last service about 5000 KM ago. The engine hesitation seems worse on cold starts and improves slightly after warming up, which makes me think even more that it could be related to a coil failure rather than spark plug issues.

Based on your error code P0301 and the symptoms getting worse during cold starts, this definitely mirrors what happened with my RS5. While my initial issue was a loose connection, it eventually progressed to a complete ignition coil failure in cylinder 1. The misfire being isolated to cylinder 1 and the fact your spark plugs are relatively new strongly points to a faulty ignition coil. In my case, after replacing just the cylinder 1 coil, all issues resolved, the engine hesitation disappeared, no more stalling at idle, and the check engine light cleared. The repair cost was around 180 Euro including parts and labor. I opted to replace just the problematic coil rather than doing all four since the others tested fine. However, if your budget allows, replacing all coils preventively might make sense given your mileage. One quick test you can try: swap the coil from cylinder 1 with another cylinder. If the misfire code moves to the new cylinder location, this confirms the ignition coil is definitely your culprit. Just ensure the engine is completely cool before attempting any coil swaps.

Thanks for the detailed feedback. I just swapped the coil from cylinder 1 with cylinder 3 as suggested, and interestingly, the vehicle diagnostics now show error code P0303, confirming the misfire followed the coil to cylinder 3. This pretty much confirms the coil failure diagnosis. Given this clear evidence and considering the mileage on my RS5, I think I will go ahead and replace all four coil packs preventively. The engine hesitation and rough idle issues are becoming quite annoying, especially during cold starts. Will book it in for repair next week, the 180 Euro estimate seems reasonable for the work needed. Really appreciate all the troubleshooting guidance. This saved me time in pinpointing the exact issue with the ignition system before heading to the workshop.