European Vehicle Turbo Performance Diagnostics

A

AutoMechSpecialist

Master Mechanic
**Vehicle:** 2016 Audi S4 B8.5, 3.0T Supercharged
**Mileage:** 88,000
**Symptoms:**
- Reduced boost pressure above 4000 RPM
- P0299 code (Underboost condition)
- No unusual noises or smoke
- Performance feels flat in upper RPM range

**Diagnostics Completed:**
- Smoke test: No visible leaks
- DV operation: Normal
- MAP sensor readings: Within spec
- Supercharger bypass: Operating correctly

Suspecting either a failing supercharger clutch or possible carbon buildup on valves. Any other areas I should investigate?
 
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On the 3.0T engine, check these common issues:

1. **Supercharger Intercooler Cores** - They can develop internal leaks that don't show on smoke tests
2. **Throttle Body Pipe** - The rubber connector between supercharger and throttle body can develop small tears
3. **PCV System** - The integrated PCV can fail and cause boost leaks
4. **Carbon Buildup** - Very common on direct injection, causes restriction at higher airflow

**Quick test:** Remove the supercharger belt and see if the issue persists. If it does, it's not the supercharger clutch. Also, log actual vs requested boost with VCDS or OBDeleven.
 
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