Audi S3 Rough Idle Points to Failing Spark Plugs

Had similar symptoms with my 2015 Audi S4. The rough idle and jerking during acceleration turned out to be a combination of failing ignition coils and fuel injectors. The diagnosis showed misfires across multiple cylinders. The main culprits were: 2 faulty ignition coils causing inconsistent spark, Clogged fuel injectors disrupting the fuel spray pattern, A worn oxygen sensor throwing off the air-fuel mixture These components working poorly together created a chain reaction affecting engine performance. The crankshaft sensor readings were also erratic due to the uneven running. For proper repair, all ignition coils were replaced as a set since they had similar wear. The fuel injectors needed professional cleaning and the oxygen sensor was replaced. This resolved both the rough idle and acceleration issues. This was a serious issue that needed immediate attention to prevent potential damage to the catalytic converter from the misfires. The check engine light and error codes in these cases are warning signs that shouldnt be ignored. The symptoms you describe match almost exactly what happened in my case. Getting it diagnosed properly with a full computer scan would be the first step to confirm if its the same underlying issues.

Thanks for sharing your experience. Pretty much the same happened to my S3 last year, the engine misfire was causing rough idle and jerking. My mechanic also found bad ignition coils and clogged injectors. Just wondering how much you ended up paying for the full repair? Also curious if youve had any related issues pop up since getting it fixed? The timing belt was also quite worn in my case so I had that replaced while they were at it, though at my mileage it was probably due anyway.

After getting everything sorted, the total repair came to 265 Euro to fix the exhaust leak that was contributing to the engine misfire issues. The uneven engine running completely cleared up after the work was done. Since the repair, the engine has been running smooth with no issues. The original symptoms of rough idle and jerking during acceleration are completely gone. The check engine light hasnt returned either, which confirms the mechanic properly diagnosed and fixed the root cause. Having a proper diagnosis made all the difference. When multiple components like spark plugs, ignition coils and fuel injectors start wearing out together, it can create complex problems that need expert attention. The oxygen sensor readings are now showing normal operation, which indicates the air-fuel mixture is spot on. Going to a qualified mechanic was definitely worth it in this case. Getting everything fixed properly the first time helps prevent cascading issues that could end up being more expensive later.

Thanks again for the info. Last week I finally had my S3 fixed and wanted to share how it went. Took it to a certified shop that specializes in German cars. The engine misfire was exactly what we suspected, bad ignition coils and dirty fuel injectors. The total came to 890 Euro including parts and labor. More than I wanted to spend, but they did a thorough job. They cleaned all fuel injectors, replaced the ignition coils, and installed a new air filter since it was pretty clogged. The oxygen sensor actually tested fine in my case. The car runs perfectly now, no more rough idle or hesitation during acceleration. Looking back, I should have addressed it sooner instead of worrying about getting ripped off. The peace of mind from having it properly diagnosed and fixed was worth the cost. Best part is the check engine light is finally off after haunting my dashboard for weeks. Definitely learned my lesson about preventive maintenance this time around.