2019 Mercedes-Benz GLS450 Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2019 Mercedes-Benz GLS450 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 2019 Mercedes-Benz GLS450 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 2019 Mercedes-Benz GLS450 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 2019 Mercedes-Benz GLS450?

When diagnosing a rough idle in a 2019 Mercedes-Benz GLS450, it's essential to adopt a systematic diagnostic approach that prioritizes simpler checks before delving into more complex issues. Start by using a diagnostic scanner to check for any fault codes, as these can quickly point you to specific problems within the vehicle's systems. Next, inspect the spark plugs for wear or fouling, as they play a crucial role in engine performance. A clean air filter is also vital; ensure it is free from debris to maintain proper airflow. Additionally, check for vacuum leaks in the hoses and lines, as these can disrupt the air-fuel mixture and lead to idle issues. Don't overlook the fuel system; inspect components like the fuel filter and injectors to ensure they are functioning correctly. The throttle body should also be examined for carbon buildup, which can hinder its operation. Finally, assess the engine mounts for any signs of wear, as damaged mounts can cause vibrations that contribute to a rough idle. By following this structured approach, you can effectively identify and resolve the underlying causes of a rough idle in your GLS450.

What are the common problems that could cause a rough idle in a 2019 Mercedes-Benz GLS450?

When diagnosing a rough idle in a 2019 Mercedes-Benz GLS450, it's crucial to explore several common problems that may be affecting the vehicle's performance. A dirty or faulty mass airflow sensor is often a primary suspect, as it can disrupt the air-fuel mixture essential for smooth engine operation. Additionally, vacuum leaks can lead to an imbalance in this mixture, resulting in an unstable idle. Worn or faulty spark plugs frequently contribute to misfires, which can further exacerbate rough idling. A clogged fuel filter may also restrict fuel flow to the engine, hindering its ability to maintain a steady idle. Moreover, a malfunctioning oxygen sensor can interfere with the air-fuel mixture, worsening the rough idle issue. Other potential culprits include problems with the Exhaust Gas Recirculation (EGR) valve and a dirty or faulty throttle body, both of which can significantly impact engine performance. By systematically checking these components, DIY enthusiasts can effectively troubleshoot and potentially resolve the rough idle issue in their GLS450, ensuring a smoother driving experience.

How urgent is it to address the rough idle in my 2019 Mercedes-Benz GLS450?

Addressing a rough idle in your 2019 Mercedes-Benz GLS450 is not just a matter of comfort; it is crucial for the overall health of your vehicle. A rough idle can indicate serious underlying issues, such as problems with the fuel or ignition systems, which, if left unchecked, may lead to decreased fuel efficiency and increased emissions. Moreover, ignoring this symptom can escalate into more severe engine problems, resulting in costly repairs that could have been avoided with timely intervention. Regular maintenance and prompt attention to any irregularities in your vehicle's performance are essential to prevent further damage and ensure a smooth driving experience. Therefore, if you notice a rough idle, it is imperative to address it as soon as possible to safeguard your vehicle's performance and longevity.

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