2020 Mercedes-Benz GLC63 AMG Has Rough Idle

Diagnosing the Causes of Rough Idle in Your 2020 Mercedes-Benz GLC63 AMG and How to Resolve Them

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Reviewed by
Aisha
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 2020 Mercedes-Benz GLC63 AMG 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 2020 Mercedes-Benz GLC63 AMG 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.

Brake caliper failure occurs in two different ways, and they create different symptoms.

The caliper can become stuck, in which case it won't release the brake pads. The seized caliper will cause the vehicle to brake constantly on one side, forcing the car to move toward that side. This pulling will be accompanied by a strong odor from one wheel.

Another way calipers fail is by leaking. If the caliper leaks, the brake pedal will feel too easy to push, and will sink all the way to the floor when held. Braking will become less effective the longer this goes on. There may also be brake fluid leaking onto the wheel.

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.

Brake rotors are mainly maintenance free, but when they have been subjected to abnormally hard use, the heat they absorb can cause the metal to turn blue, and cracking to occur. When this occurs, customers often specify they have lost braking power, or the vehicle's brakes are making noise. There may be no symptoms at all related to changing the brake rotors, since it is recommended to change brake rotors on most modern vehicles when performing a standard brake service.

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 diagnostic steps to take for a rough idle in a 2020 Mercedes-Benz GLC63 AMG?

When addressing a rough idle in your 2020 Mercedes-Benz GLC63 AMG, it's essential to adopt a methodical diagnostic approach. Start by checking for any illuminated check engine lights, as these can provide crucial error codes through an OBD-II scanner, guiding you to the specific issue. Next, inspect the spark plugs for wear or fouling, as these components are vital for proper engine performance; replacing any damaged plugs can often resolve misfires that contribute to rough idling. Following this, examine the air filter for clogs, as restricted airflow can significantly impact engine efficiency. Don’t overlook the fuel system; ensure that the fuel filter is clean and that the injectors are functioning correctly, as blockages here can lead to uneven idling. Cleaning the throttle body is another critical step, as carbon buildup can disrupt the air-fuel mixture. Additionally, inspect vacuum hoses for leaks, which can create air imbalances affecting idle quality. Finally, assess the mass airflow sensor for dirt or damage, as a malfunctioning sensor can lead to incorrect air measurements, further complicating idle issues. By systematically following these steps, you can effectively diagnose and address the rough idle in your vehicle, ensuring optimal performance.

What are the common problems that could cause a rough idle in a 2020 Mercedes-Benz GLC63 AMG?

When dealing with a rough idle in your 2020 Mercedes-Benz GLC63 AMG, it's crucial to understand the common problems that may be at play. One of the primary culprits could be dirty or faulty spark plugs, which can cause misfiring and lead to an uneven idle. Additionally, vacuum leaks in the intake system can disrupt the delicate air-fuel mixture, exacerbating the rough idle issue. Another potential problem is a malfunctioning mass airflow sensor, which plays a vital role in regulating the engine's air-fuel ratio; if it fails, you may notice significant idling issues. A clogged fuel filter can also restrict fuel flow, resulting in poor engine performance and rough idling. Furthermore, a faulty oxygen sensor can mismanage the air-fuel mixture, contributing to the problem. Lastly, issues with the Exhaust Gas Recirculation (EGR) valve can lead to improper exhaust gas recirculation, further complicating the idle situation. Addressing these issues promptly is essential not only for restoring smooth operation but also for preventing more severe damage to your vehicle.

How urgent is it to address the rough idle in a 2020 Mercedes-Benz GLC63 AMG?

Addressing a rough idle in your 2020 Mercedes-Benz GLC63 AMG is not just a matter of comfort; it is crucial for the overall health and performance of your vehicle. A rough idle can indicate underlying problems such as dirty fuel injectors, a clogged air filter, or faulty spark plugs, which, if left unattended, can lead to more severe issues like engine misfires and decreased fuel efficiency. Ignoring these symptoms may result in significant damage to engine components over time, potentially leading to costly repairs. Therefore, it is essential to prioritize resolving a rough idle promptly to ensure your vehicle operates smoothly and efficiently, safeguarding both your investment and your safety on the road.

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2020 Mercedes-Benz GLC63 AMG Rough Idle Causes & Solutions