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2020 QX50 VC-Turbo - Metallic Rattle on Cold Start/Acceleration

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Diana O. · rep 0 · May 22, 5:04 AM · 1 replies · solved · Question

Vehicle: 2020 Infiniti QX50 Essential

Hello everyone,

I own a 2020 Infiniti QX50 Essential with about 45,000 miles. For the past few weeks, I've been hearing a distinct metallic rattling noise coming from the engine bay. It's most noticeable on a cold start, lasting for a few seconds, but it also reappears sometimes under light acceleration or when the engine is under a bit of load.

I've also noticed a slight decrease in my fuel economy, though nothing drastic. The car otherwise seems to drive fine, but the rattle is really concerning me. I know the VC-Turbo engine is complex, and I'm worried this might be a sign of a serious problem.

Has anyone with a VC-Turbo QX50 experienced this kind of rattling? What was the cause, and what did it take to fix it? Any insights would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:04 AM

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ClearTheCode admin answer:

The metallic rattling noise you're hearing from your 2020 Infiniti QX50's VC-Turbo engine, especially on cold starts and under load, is a concern that should be addressed promptly. The VC-Turbo engine is innovative but also has unique components that can be sources of noise.

Here are the most common potential causes:

  1. Timing Chain/Tensioner Issues: A common source of metallic rattling, especially on cold start, is a worn or stretched timing chain or a failing hydraulic tensioner. As oil pressure builds, the noise might subside, but it can reappear under load.
  2. Variable Compression Mechanism Components: The VC-Turbo engine's unique variable compression ratio system involves complex linkages and actuators. Wear or issues within this mechanism could potentially generate unusual noises. This is less common but specific to this engine.
  3. High-Pressure Fuel Pump (HPFP): The HPFP on direct-injection engines can sometimes produce a ticking or rattling noise, which might be more pronounced when cold or under load. While often considered normal, an excessively loud rattle could indicate an issue.
  4. Exhaust Heat Shields: Sometimes, a loose or corroded exhaust heat shield can vibrate and create a metallic rattling sound, which can be mistaken for an internal engine issue.
  5. Turbocharger Wastegate Rattle: The wastegate actuator or its linkage can sometimes develop play, leading to a rattle, especially at certain RPMs or engine loads.

When to see a shop: Given the complexity of the VC-Turbo engine, it's highly recommended to have your QX50 inspected by an Infiniti dealership or a specialist familiar with this engine. They can use diagnostic tools and their expertise to pinpoint the exact source of the rattle. Ignoring a timing chain issue can lead to severe engine damage. Early diagnosis can prevent more costly repairs.

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