2016 Mercedes-Benz GL550 Has Rough Idle

Diagnosing Causes of Rough Idle in Your 2016 Mercedes-Benz GL550 and Solutions 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 GL550 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 GL550 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 GL550?

To effectively diagnose a rough idle in your 2016 Mercedes-Benz GL550, start with a thorough inspection of the vacuum lines and connections, as any leaks or damage here can significantly impact engine performance. Next, examine the spark plugs; ensuring they are clean and functioning properly is crucial, as worn or dirty plugs can lead to misfires and rough idling. Following this, test the ignition coil to confirm it is operating correctly, since a faulty coil can disrupt the ignition process. Lastly, check the cam sensors and solenoids by removing their connectors to inspect for oil contamination, particularly on both bank connections. By following this diagnostic approach, you can systematically identify and address the underlying issues causing the rough idle, ensuring your vehicle runs smoothly.

What are the common problems that could cause a rough idle in a 2016 Mercedes-Benz GL550?

When diagnosing a rough idle in a 2016 Mercedes-Benz GL550, it's essential to consider several common problems that could be affecting the 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 in the intake system can introduce unmetered air, leading to an uneven idle. Another critical component to inspect is the oxygen sensor; if it's malfunctioning, it can throw off the air-fuel ratio, further exacerbating idle issues. A clogged fuel filter may also be a factor, as it can restrict fuel flow, impacting engine performance at idle. Furthermore, worn or fouled spark plugs can cause misfires, contributing to a rough idle experience. Lastly, a malfunctioning throttle body can disrupt airflow into the engine, resulting in similar symptoms. By addressing these potential issues through regular maintenance and timely repairs, you can significantly improve the idle quality of your GL550.

How urgent is it to address the rough idle in my 2016 Mercedes-Benz GL550?

Addressing a rough idle in your 2016 Mercedes-Benz GL550 is not just a matter of convenience; it is crucial for maintaining the overall health and performance of your vehicle. Ignoring this symptom can lead to serious engine problems, such as misfiring cylinders or sensor failures, which may escalate into costly repairs if left unaddressed. Additionally, a rough idle can significantly impact your fuel efficiency, causing your vehicle to consume more gas than necessary, which not only affects your wallet but also increases your carbon footprint. Furthermore, if your vehicle struggles with a rough idle, it may fail emissions tests, leading to legal and environmental repercussions. Lastly, a smooth idle is essential for a comfortable driving experience, ensuring that you and your passengers enjoy a pleasant ride. Therefore, it is imperative to address any rough idle issues promptly to avoid further complications and ensure your Mercedes-Benz GL550 operates at its best.

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2016 Mercedes-Benz GL550 Rough Idle: Causes & Repair Costs