Mercedes-Benz CLS63 AMG S Has Rough Idle

Diagnosing the Causes of Rough Idle in Your Mercedes-Benz CLS63 AMG S and How to Resolve Them

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Reviewed by
Andrew Hajjar
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 Mercedes-Benz CLS63 AMG S 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 Mercedes-Benz CLS63 AMG S 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.

Troubleshooting Rough Idle in a Mercedes-Benz CLS63 AMG S

When troubleshooting a rough idle in your Mercedes-Benz CLS63 AMG, it's essential to adopt a systematic diagnostic approach. Start by inspecting for a vacuum leak, as this is a prevalent issue that can significantly affect engine performance. Check all vacuum hoses and connections for any signs of wear or disconnection. Next, examine the spark plugs; worn or fouled plugs can disrupt the combustion process, leading to an uneven idle. If the spark plugs appear to be in good condition, turn your attention to the ignition coils, as faulty coils can cause misfires and contribute to rough idling. Look for any warning lights on the dashboard, particularly the check engine light, which can provide valuable diagnostic information. By methodically assessing these components, you can effectively identify and resolve the underlying issues causing the rough idle, ensuring your CLS63 AMG runs smoothly.

Troubleshooting Rough Idle in a Mercedes-Benz CLS63 AMG S

When troubleshooting a rough idle in your Mercedes-Benz CLS63 AMG S, it's essential to consider several common problems that could be affecting your vehicle's performance. One of the primary issues could be a vacuum leak, which disrupts the air-fuel mixture and leads to an unstable idle. Additionally, worn or faulty spark plugs can cause misfires, contributing to a rough idle as they fail to ignite the fuel properly. Another potential culprit is a malfunctioning ignition coil, which is crucial for delivering the necessary spark to the engine. If the fuel injectors are leaking, this can also result in an uneven idle, particularly noticeable when the engine is cold. Lastly, the condition of the engine mounts should not be overlooked, as worn mounts can lead to excessive engine movement, further exacerbating idle issues. By systematically checking these components, you can identify the root cause of the rough idle and take the necessary steps to resolve it, ensuring your CLS63 AMG S runs smoothly.

Why is My Mercedes-Benz CLS63 AMG S Idling Rough and What Should I Do?

When your Mercedes-Benz CLS63 AMG S is idling roughly, it’s crucial to act swiftly, as ignoring this symptom can lead to more severe engine problems and safety risks. A damaged piston or low boost issues related to the ECU, wastegate, or vacuum system can significantly impact engine performance, potentially resulting in costly repairs if left unaddressed. Regular maintenance is essential, especially for high-performance models like the CLS63 AMG S, where neglecting oil changes and other routine services can exacerbate existing issues. By prioritizing a thorough inspection by a qualified mechanic, you can identify the root cause of the rough idling and take corrective measures before the situation escalates. Remember, timely action not only preserves the integrity of your vehicle but also ensures a safer driving experience.

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