2023 Mercedes-Benz GLS450 Has Rough Idle

Resolve Rough Idle in Your 2023 Mercedes-Benz GLS450 for a Smoother Ride

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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 2023 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 2023 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.

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 2023 Mercedes-Benz GLS450?

When diagnosing a rough idle in a 2023 Mercedes-Benz GLS450, it's crucial to follow a structured diagnostic approach that prioritizes simpler checks before delving into more complex issues. Begin by utilizing a diagnostic scanner to identify any fault codes, as these can provide immediate insights into potential problems affecting engine performance. Next, inspect the spark plugs for signs of wear or fouling, since these components play a vital role in ignition and can lead to misfires if compromised. Afterward, check the air filter to ensure it is clean and free from obstructions, as a clogged filter can restrict airflow and contribute to rough idling. It's also important to evaluate the fuel system for any clogs or malfunctions, as proper fuel delivery is essential for smooth engine operation. Pay attention to the vacuum hoses as well; any cracks or disconnections can result in vacuum leaks, which are often responsible for rough idling. Lastly, examine the throttle body and intake manifold for carbon buildup or leaks that could disrupt the air-fuel mixture. By systematically addressing these areas, you can effectively diagnose and resolve the rough idle issue, ensuring optimal performance of your GLS450.

What are the common problems that could cause a rough idle in a 2023 Mercedes-Benz GLS450?

When dealing with a rough idle in your 2023 Mercedes-Benz GLS450, it's essential to understand the common problems that could be at play. One frequent culprit is a dirty or faulty mass airflow sensor, which can disrupt the delicate balance of air and fuel entering the engine, leading to an uneven idle. Additionally, vacuum leaks can create an improper air-fuel mixture, exacerbating the rough idle issue. It's also worth checking the condition of your spark plugs and ignition coils, as worn components can cause misfires that manifest as a rough idle. A clogged fuel filter may restrict fuel flow, further impacting engine performance at idle. Furthermore, issues with the Exhaust Gas Recirculation (EGR) valve can affect idle quality, as can a malfunctioning throttle body that disrupts air intake. By systematically inspecting these components, you can identify and address the root cause of the rough idle, ensuring your GLS450 runs smoothly.

How urgent is it to address the rough idle in my 2023 Mercedes-Benz GLS450?

Addressing a rough idle in your 2023 Mercedes-Benz GLS450 is not just a matter of comfort; it is essential for the overall health of your vehicle. A rough idle can signal serious underlying problems within the engine, fuel system, or ignition system, which, if left unchecked, may escalate into more significant issues that could compromise your vehicle's performance and safety. Ignoring this symptom can lead to decreased fuel efficiency, engine misfires, and even costly damage to critical engine components. Moreover, regular maintenance and prompt repairs are key to avoiding more extensive and expensive repairs in the future. Therefore, it is highly advisable to have a qualified mechanic diagnose and resolve the rough idle as soon as possible. By taking swift action, you not only enhance the longevity of your Mercedes-Benz GLS450 but also ensure a safer and more efficient driving experience.

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2023 Mercedes-Benz GLS450 Rough Idle Causes & Repairs