2020 Mercedes-Benz GLC43 AMG Has Rough Idle

Diagnosing the Causes of Rough Idle in Your 2020 Mercedes-Benz GLC43 AMG and How to Resolve Them

Find Repair Location
Reviewed by
Bo Fader
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 GLC43 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 GLC43 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 steps to diagnose a rough idle in a 2020 Mercedes-Benz GLC43 AMG?

To effectively diagnose a rough idle in your 2020 Mercedes-Benz GLC43 AMG, start with a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. Begin by using an OBD-II scanner to identify any error codes, as these can pinpoint specific issues affecting engine performance. Next, inspect the spark plugs for wear or fouling, as these components are crucial for proper combustion. A clean air filter is also essential; ensure it is free from dirt and debris that could restrict airflow. Following this, examine the fuel system, including the fuel filter and injectors, to rule out any clogs or malfunctions that could disrupt fuel delivery. Don’t overlook the vacuum hoses; check for cracks or leaks that might affect the air-fuel mixture. Additionally, test the mass airflow sensor, as a faulty sensor can significantly impact idle quality. Finally, inspect the throttle body for cleanliness and functionality, as any buildup or malfunction here can also lead to rough idling. By following this structured diagnostic approach, you can efficiently identify and resolve the underlying causes of a rough idle in your vehicle.

What are the common problems that could cause a rough idle in a 2020 Mercedes-Benz GLC43 AMG?

When dealing with a rough idle in your 2020 Mercedes-Benz GLC43 AMG, it's essential to consider several common problems that could be at play. One of the primary culprits is a dirty or faulty mass airflow sensor, which can disrupt the delicate balance of the air-fuel mixture, leading to an unstable idle. Additionally, vacuum leaks can create an improper air-fuel ratio, further exacerbating the rough idle issue. Worn or faulty spark plugs are another frequent cause, as they can lead to engine misfires that manifest as rough idling. A clogged fuel filter may also restrict fuel flow, impacting engine performance and contributing to the problem. Furthermore, issues with fuel injectors, whether due to clogging or malfunction, can disrupt fuel delivery, resulting in an uneven idle. Lastly, a faulty oxygen sensor can significantly affect the air-fuel mixture, leading to poor engine performance and rough idling. By identifying and addressing these common issues, you can effectively restore your vehicle's smooth operation and enhance its overall performance.

How urgent is it to address the rough idle in a 2020 Mercedes-Benz GLC43 AMG?

When dealing with a rough idle in your 2020 Mercedes-Benz GLC43 AMG, it’s crucial to understand the urgency of the situation. While the rough idle may not seem like an immediate threat, neglecting this symptom can lead to more severe issues down the line, such as engine misfires or decreased fuel efficiency. These problems not only affect your vehicle's performance but can also result in costly repairs if left unaddressed. For DIY enthusiasts, it’s advisable to start with a thorough inspection of the fuel injectors, air filter, and spark plugs, as these components are often the culprits behind a rough idle. Additionally, consider checking the oxygen sensor, as its malfunction can significantly impact engine performance. By taking proactive steps to diagnose and resolve the issue, you can ensure the longevity and optimal functioning of your vehicle, ultimately saving you time and money in the long run.

You’ve got options with RepairPal

Whether you need a more accurate auto repair estimate or help finding a reputable shop in your area, we’ve got you covered.