2018 Mercedes-Benz S560 Has Rough Idle

Causes of Rough Idle in 2018 Mercedes-Benz S560 and Solutions for Smoother Performance

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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 2018 Mercedes-Benz S560 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 2018 Mercedes-Benz S560 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 initial diagnostic steps to take for a rough idle in a 2018 Mercedes-Benz S560?

When faced with a rough idle in your 2018 Mercedes-Benz S560, the first step is to check for error codes using a diagnostic scanner. This tool can reveal specific issues logged in the vehicle's computer, guiding your next steps. Following this, inspect the spark plugs for any signs of wear or fouling, as these can lead to misfires that contribute to an unstable idle. Next, examine the air filter; a clogged filter can restrict airflow, negatively impacting engine performance. It's also crucial to inspect the vacuum hoses for any cracks or leaks, as these can disrupt the air-fuel mixture. Additionally, take a look at the fuel system, including the fuel filter and injectors, since blockages or malfunctions here can also cause rough idling. Lastly, don't forget to check the throttle body for carbon buildup or dirt, which can hinder airflow. By systematically addressing these areas, you can effectively diagnose and potentially resolve the rough idle issue in your vehicle.

What are the common problems that could cause a rough idle in a 2018 Mercedes-Benz S560?

When diagnosing a rough idle in a 2018 Mercedes-Benz S560, it's essential to consider several common problems that could be affecting your vehicle's performance. One of the primary culprits is a dirty or faulty mass airflow sensor, which can disrupt the delicate balance of the air-fuel mixture necessary for smooth engine operation. Additionally, vacuum leaks can create an imbalance in this mixture, leading to instability during idling. Worn or faulty spark plugs are another frequent issue, as they can cause misfires that contribute to a rough idle. Furthermore, a clogged fuel filter may restrict fuel flow, impacting engine performance and causing roughness at idle. Issues with fuel injectors can also lead to improper fuel delivery, exacerbating the problem. Lastly, a malfunctioning oxygen sensor can significantly affect the air-fuel mixture, resulting in rough idling and other performance-related issues. By addressing these potential problems through regular maintenance and timely repairs, you can restore your S560's smooth operation and enhance its overall performance.

How urgent is it to address the rough idle in my 2018 Mercedes-Benz S560?

Addressing a rough idle in your 2018 Mercedes-Benz S560 is crucial for maintaining the vehicle's overall health and performance. Ignoring this symptom can lead to serious engine problems, such as misfiring cylinders or fuel system malfunctions, which may escalate into costly repairs if left unattended. Additionally, a rough idle can significantly affect your fuel efficiency, leading to increased fuel consumption and higher costs at the pump. Beyond financial implications, a rough idle can also compromise your driving comfort, causing vibrations that detract from the smooth experience expected from a luxury vehicle. Most importantly, delaying repairs can result in further damage, potentially putting your safety at risk. Therefore, it is advisable to address any rough idle symptoms promptly to ensure your Mercedes-Benz operates optimally and to avoid more severe issues down the line.

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