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I have this weird issue with my 2011 Mitsubishi Lancer 2.0L SE. When I am maintaining a speed by feathering/light load the accelerator, I get this metallic rattling noise from under the hood. Going 50kmh, 1250-1500 RPM. Some things to note:

  1. Sound is not present when accelerating or when "under load"
  2. Sound is not present when revving in park or neutral, only in drive
  3. Sound is louder on hot, dry days or after the engine has warmed

Any ideas? Mitsubishi dealer is useless and charges me to not find and fix the issue.

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  • Welcome to Motor Vehicle Maintenance & Repair! Jun 25, 2018 at 21:05

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I suspect the noise is caused by a loose exhaust pipe or shield, which under certain conditions (when you've "feathered" the throttle) vibrates and hits an adjacent piece of metal.

Check the exhaust pipe mounts; they are often rubber and degrade with age and use. Check also the mounting of any sheet metal shielding that is adjacent to the exhaust. While you hear this noise from under the hood, it's possible that the fault is further aft in the exhaust system, so check the mounts under the car as well.

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    Along with the suggestion in the above answer, consider to not "rev" the engine, but to observe and listen under the hood while someone else gradually and gently increases the throttle in park or neutral with the handbrake applied. David's answer is certainly a good one, and the gentle increase my locate a specific rpm in which the loose part will vibrate.
    – fred_dot_u
    Jun 25, 2018 at 18:11

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