2021 Mercedes-Benz AMG GT Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2021 Mercedes-Benz AMG GT and How to Resolve Them

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Reviewed by
Devin Cabugcal
Written by RepairPal Car Genius
Updated January 14, 2025
0%
21% chance it's the
Spark Plugs
0%
15% chance it's the
Ignition Coil
0%
64% chance it's
Something else
The most common reasons a 2021 Mercedes-Benz AMG GT has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
  • Spark Plugs: Worn or fouled spark plugs can lead to misfires, poor fuel economy, and difficulty starting the engine.
  • Ignition Coil: A faulty ignition coil can cause misfires, rough idling, and difficulty starting the engine due to inadequate spark delivery to the spark plugs.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a 2021 Mercedes-Benz AMG GT has rough idle?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

Here are a few common symptoms of worn-out brake pads:

  1. Low brake pad warning light is on: Not all vehicles are equipped with this system, but if yours is, this dashboard indicator light will likely be the first signal it’s time to replace your brake pads.
  2. Brakes start to squeal regularly: This is often one of the first signs of worn brake pads and is caused by a metallic piece built into brake pads for this exact purpose. This part contacts the brake rotor to make a squealing or whining noise when the pads are low.
  3. Brakes make loud grinding noise: If not addressed early enough, your brake pads may get so worn that the metal backing plate of the pad grinds against the metal rotor.
  4. Brake pads look thin: You may be able to visually check your brake pad thickness to determine if they need replacement.

Most often, a brake system inspection will just be a routine portion of manufacturer specified maintenance, and will be performed at mileage intervals. In those cases, there will likely be no symptoms. However, when a brake system makes a funny noise, causes vibration, is hard to use, will not slow the vehicle, prevents the vehicle from driving, makes the vehicle pull to one side, or leaks brake fluid, the vehicle will need a visit dedicated to the inspection of the brake system.

What are the steps to diagnose a rough idle in a 2021 Mercedes-Benz AMG GT?

To effectively diagnose a rough idle in your 2021 Mercedes-Benz AMG GT, start with a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Begin by using an OBD-II scanner to check for any error codes, as these can quickly highlight potential issues within the engine management system. Next, inspect the spark plugs for wear or fouling, since these components are crucial for proper combustion and can lead to misfires if compromised. Following this, evaluate the air intake system for leaks or clogs, as any disruption here can significantly affect engine performance. Don’t overlook the fuel system; check the fuel filter and injectors for clogs or malfunctions that could hinder fuel delivery. Additionally, inspect all vacuum hoses for cracks or disconnections, as vacuum leaks can lead to erratic engine behavior. Testing the mass airflow sensor is also essential, as a faulty sensor can provide incorrect readings that disrupt the air-fuel mixture. Finally, examine the throttle body for carbon buildup or operational issues, as a clean and functioning throttle body is vital for maintaining smooth airflow. By following this diagnostic approach, you can effectively identify and address the root cause of the rough idle in your vehicle.

What are the common causes of a rough idle in a 2021 Mercedes-Benz AMG GT?

When dealing with a rough idle in your 2021 Mercedes-Benz AMG GT, it's crucial to understand the common problems that could be at play. Start by checking the air filters; a dirty or clogged filter can significantly restrict airflow to the engine, leading to performance issues. Next, inspect the spark plugs, as worn or faulty plugs can cause misfiring, which directly affects idle smoothness. Additionally, look for any vacuum leaks, as these can disrupt the air-fuel mixture, further complicating engine performance. Fuel system components, including the fuel filter and injectors, should also be examined, as clogs can hinder fuel delivery. Don't overlook the oxygen sensor; a malfunction here can lead to an improper air-fuel ratio, resulting in a rough idle. Lastly, consider the throttle body, as carbon buildup or sensor issues can interfere with air intake. By systematically addressing these areas, you can enhance your vehicle's performance and restore a smooth idle.

How urgent is it to address the rough idle in a 2021 Mercedes-Benz AMG GT?

Addressing a rough idle in your 2021 Mercedes-Benz AMG GT is not just a matter of comfort; it is crucial for the vehicle's overall health and performance. A rough idle can indicate underlying problems within the engine or fuel system, which, if ignored, may escalate into more severe issues such as engine misfires or decreased fuel efficiency. These complications can lead to costly repairs and even significant engine damage over time. Therefore, it is essential to take immediate action when you notice this symptom. By addressing the rough idle promptly, you not only enhance your driving experience but also safeguard your investment, ensuring that your AMG GT continues to perform optimally for years to come. Ignoring this issue could compromise your vehicle's reliability and safety, making it imperative to prioritize its resolution.

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2021 Mercedes-Benz AMG GT Rough Idle Causes & Repairs