2016 Mercedes-Benz S550 Has Rough Idle

Resolve Rough Idle in Your 2016 Mercedes-Benz S550 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 2016 Mercedes-Benz S550 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 2016 Mercedes-Benz S550 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 2016 Mercedes-Benz S550?

To effectively diagnose a rough idle in your 2016 Mercedes-Benz S550, it's essential to adopt a systematic diagnostic approach that begins with simpler checks before progressing to more complex issues. Start by utilizing a diagnostic scanner to identify any fault codes stored in the vehicle's computer system, as these codes can provide immediate insights into potential problems. Next, inspect the spark plugs for signs of wear or fouling, since compromised spark plugs can lead to misfires and contribute to a rough idle. Following this, check the air filter; ensuring it is clean is vital for optimal airflow, as a clogged filter can significantly hinder engine performance. After these initial checks, examine the vacuum hoses for any cracks or leaks, which can disrupt the air-fuel mixture and exacerbate idle issues. Additionally, assess the fuel system components, including the fuel filter and injectors, as blockages or malfunctions here can also affect engine performance. It’s also important to test the mass airflow sensor, since a faulty sensor can lead to an incorrect air-fuel mixture. Lastly, inspect the throttle body for any carbon buildup or dirt that may impede its function. By following this structured approach, you can efficiently pinpoint and address the root causes of a rough idle in your vehicle, ensuring a smoother driving experience.

What are the common causes of a rough idle in a 2016 Mercedes-Benz S550?

When dealing with a rough idle in your 2016 Mercedes-Benz S550, it's crucial to understand the common problems that could be at play. One of the primary culprits is dirty or faulty spark plugs, which can lead to engine misfires and an uneven idle. Additionally, vacuum leaks can significantly disrupt the air-fuel mixture, causing instability in engine performance. Another potential issue is a malfunctioning mass airflow sensor, which can throw off the air-fuel ratio and contribute to rough idling. It's also important to check the fuel filter; a clogged filter can restrict fuel flow, leading to similar symptoms. Lastly, problems with the idle air control valve can affect the engine's idle speed, resulting in a rough idle. By systematically inspecting these components, you can identify and address the root cause of the rough idle, ensuring your S550 runs smoothly.

How urgent is it to address the rough idle issue in my 2016 Mercedes-Benz S550?

Addressing the rough idle issue in your 2016 Mercedes-Benz S550 is not just a matter of convenience; it is crucial for maintaining the health and performance of your vehicle. Ignoring this symptom can lead to escalating engine problems, which may result in costly repairs down the line. Additionally, a rough idle can significantly impact your fuel efficiency, causing you to spend more on gas than necessary, which is an avoidable expense. Moreover, this issue can affect your vehicle's emissions, potentially leading to failures in emissions tests and contributing to environmental pollution. Lastly, a rough idle detracts from your driving comfort, making each journey less enjoyable. Therefore, it is essential to address this issue promptly to avoid further complications and ensure that your Mercedes-Benz S550 operates smoothly and efficiently.

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