2021 Audi RS4 Problems: 1 Issues Every Owner Should Know
2021 model year · NHTSA recalls, manufacturer TSBs, and owner forum reports · Updated May 2026
According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 2021 Audi RS4 has 1 documented known issues. No issues are rated critical, indicating generally reliable ownership. Across all issues, repair costs range from $1,000 to $1,800. DIY maintenance guides at au7o.io.
All 1 Known Issues
On the 2018-2023 Audi RS4 2.9T, the 2.9T twin-turbo V6 in RS4 Avant and RS5 (2018-2023) suffers from carbon buildup on intake valves due to direct injection. Similar to other Audi DI engines, oil vapors from PCV system bake onto valve backs. The twin-turbo setup and high performance accelerate carbon accumulation. Over 60,000 miles, carbon causes rough idle, misfires, and power loss. RS246.com forums recommend walnut blasting every 60,000 miles. The V6 configuration requires removing both intake manifolds, costing $1,000-$1,800. Audi's official recommendation is to drive hard regularly to burn off carbon—not baby the RS.
Common Symptoms
- Rough idle
- Hesitation on acceleration
- Power loss
- Poor fuel economy
- Check engine light with misfire codes
- Runs rough when cold
How to Fix
WALNUT BLASTING: Remove intake manifolds and blast walnut shells through intake ports ($1,000-$1,800 for V6). Repeat every 60,000 miles. PREVENTION: Install dual catch cans ($400-$700). Add Liqui Moly Intake Valve Cleaner to every oil change. Change oil every 5,000 miles. Drive hard regularly—Audi's recommendation.
What Owners Are Using
Parts and tips from 0+ owners who fixed this issue
- Upgrade034 Motorsport Catch Can Kit for EA839 (034-101-1016 PCV side, 034-101-1018 CCV side). Direct-fit for B9 RS4/RS5 2.9T twin-turbo V6. Lifetime warranty. (034 Motorsport #034-101-1016)
- TipThe 2.9T EA839 has both port and direct injection, which significantly reduces carbon buildup compared to older pure-DI engines. Still benefits from catch can installation.
- TipWalnut blasting interval can be extended to 70,000-100,000 miles on dual-injection 2.9T compared to 50,000 miles on older single-injection engines.
- NoteTuned RS4/RS5 cars running higher boost produce more crankcase pressure, accelerating carbon buildup. Catch can is especially important on tuned applications.