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2018 Audi A4 2.0T: Wastegate Rattle and Loss of Power

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Chris P. · rep 0 · May 22, 4:25 AM · 1 replies · solved · Question

Vehicle: 2018 Audi A4 2.0T Quattro Premium Plus

Hey everyone,

I've got a 2018 Audi A4 2.0T Quattro, and lately, I've noticed a distinct rattling sound coming from the engine bay, especially when I let off the throttle. It sounds like it's coming from the turbo area.

More concerning, I've felt a noticeable drop in power, almost like the turbo isn't spooling up correctly. Sometimes, I even get a check engine light that flashes briefly and then goes away, but I haven't been able to pull a code yet. Has anyone experienced this with their B9 A4? Could it be a wastegate issue or something more serious with the turbo itself? Any advice on what to check first would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:25 AM

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ClearTheCode admin answer:

It sounds like you're describing a common issue with the IHI turbochargers found in many Audi 2.0T engines, particularly concerning the wastegate actuator or its linkage. The rattling noise and loss of power are strong indicators.

  1. Identify the Noise Source: Carefully listen to pinpoint the exact location of the rattle. It's often most noticeable during deceleration or when the engine is idling after a drive.
  2. Check for OBD Codes: Even if the light flashes briefly, a pending code might be stored. Use an OBD-II scanner to check for codes like P0299 (Turbocharger/Supercharger Underboost) or P0234 (Turbocharger/Supercharger Overboost). These codes directly point to turbo performance issues.
  3. Inspect Wastegate Linkage: With the engine off and cool, visually inspect the wastegate actuator arm and its connection to the turbo. Look for any looseness, excessive play, or signs of wear. Sometimes, the rod connecting the actuator to the wastegate flapper can become worn or bent.
  4. Vacuum Lines: Ensure all vacuum lines connected to the wastegate actuator and N75 valve (boost control solenoid) are intact and free of cracks or leaks.

Common Causes:

  • Worn Wastegate Bushings/Flapper: Over time, the pivot points for the wastegate flapper can wear, causing it to rattle.
  • Faulty Wastegate Actuator: The actuator itself might be failing to hold boost pressure correctly or has internal wear.
  • Turbocharger Issues: Less commonly, but still possible, internal turbo damage could be contributing.

When to See a Shop: If you're experiencing consistent power loss, a persistent check engine light, or if the rattling becomes louder and more frequent, it's crucial to have a qualified Audi specialist diagnose the issue. Ignoring a failing wastegate can lead to further turbo damage or reduced engine efficiency. A shop can perform a proper boost leak test, check turbo shaft play, and confirm wastegate operation with specialized tools.

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