RS3 Engine Mount Issues Causing Rough Idle & Errors

Based on my medium-level experience working on Audis, I encountered a similar issue with my 2021 S3. The symptoms you describe match what I experienced, unusual vibrations and rough idling that felt off compared to the normal engine behavior. The root cause in my case was a failed mount connection due to a loose cable harness. The vibration issues were initially misleading, as they presented like a typical rubber mount failure. However, the workshop discovered the actual problem was a defective plug connection to the mounting bracket sensor. The repair took about 2 hours and cost 95 Euro, which included diagnostics and fixing the connection. This was much better than replacing the entire transmission mount assembly, which was my initial concern. Before suggesting more specific solutions, it would help to know: Are the vibrations more noticeable in specific gears? Does the rough idle change with engine temperature? Have you noticed any unusual sounds along with the vibrations? What are the specific error codes stored? These details would help determine if your issue matches what I experienced or if you might be dealing with an actual failed mount situation.

Last serviced at 147903KM. Can confirm the vibrations are consistently present across all gears, though more noticeable in 1st and reverse. Temperature doesnt seem to affect the idle behavior. The mounting bracket inspection revealed significant wear on the passenger side mount. Also getting a metallic clunking sound during acceleration, which seems consistent with mount failure symptoms described by others. Error codes point to powertrain-related issues: P0117 and P1234. Definitely worse than when I first posted. Planning to replace both the engine and transmission mount as preventive maintenance since labor costs will be similar either way.

Thanks for those additional details. The symptoms you're describing are even more aligned with my experience now. When my S3 developed these issues, I also noticed that distinctive metallic clunking during acceleration which turned out to be a clear indicator of mount failure. The error codes you mentioned, combined with the clunking noise and consistent vibrations, strongly suggest this is more than just the harness issue I initially dealt with. The significant wear you found on the passenger side mount matches the typical failure pattern I've seen in these models. I opted for the same approach you're considering, replacing both the engine and transmission mount simultaneously. The rubber mount degradation tends to occur at similar rates, so this preventive approach made sense. Total cost was around 450 Euro for parts and 380 Euro for labor. One thing to watch for: make sure they inspect the mounting bracket integrity during replacement. In my case, they found hairline stress fractures in the bracket itself, which could have caused problems later if not addressed during the mount replacement. The repair completely resolved my vibration issues and that annoying clunking sound. Given your higher mileage compared to when I did mine, this comprehensive replacement approach is definitely the right call.

Thanks for all the helpful input. After reading through the responses and comparing with my situation, I'm convinced this is definitely a mount failure issue that needs addressing. Given my car's mileage at 147903KM and the symptoms getting worse, replacing both the engine mount and transmission mount makes the most sense financially and practically. The metallic clunking during acceleration has become more pronounced since my initial post, which matches what others experienced with mount failure. The consistent vibrations across all gears and the stored error codes P0117 and P1234 further confirm this diagnosis. Will schedule the complete mount replacement next week. Good tip about checking the mounting bracket integrity, will make sure they inspect for stress fractures during the repair. The total cost of around 830 Euro for both mounts, including labor, seems reasonable given the comprehensive work involved. Really appreciate the detailed insights about this issue. Will update once the repair is completed.