2015 Mercedes-Benz E250 Has Rough Idle

Resolve Rough Idle in Your 2015 Mercedes-Benz E250 for a Smoother Ride

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Reviewed by
Devin Cabugcal
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 2015 Mercedes-Benz E250 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 2015 Mercedes-Benz E250 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 2015 Mercedes-Benz E250?

When addressing a rough idle in your 2015 Mercedes-Benz E250, it's essential to adopt a systematic diagnostic approach that begins with the simplest checks before progressing to more complex issues. Start by using a diagnostic scanner to check for any fault codes stored in the vehicle's computer system, as these codes can provide critical insights into the problem. Next, inspect the spark plugs for wear or fouling, as these components play a vital role in engine performance. A clean and unobstructed air filter is also crucial; ensure it is free of debris to maintain proper airflow. Additionally, examine the vacuum lines for any signs of leaks, as these can disrupt the air-fuel mixture and contribute to a rough idle. Don't overlook the fuel system; check the fuel filter and injectors to ensure they are functioning correctly, as poor fuel delivery can lead to idling issues. Finally, inspect the throttle body for carbon buildup or dirt, which can impede airflow and exacerbate the rough idle. By following this structured approach, you can effectively identify and address the underlying causes of the rough idle in your vehicle.

What are the common problems that could cause a rough idle in a 2015 Mercedes-Benz E250?

When dealing with a rough idle in a 2015 Mercedes-Benz E250, 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, leading to an unstable idle. Additionally, vacuum leaks can create an improper air-fuel ratio, further exacerbating the rough idle issue. Worn or faulty spark plugs are another frequent cause, as they can lead to engine misfires that manifest as rough idling. A clogged fuel filter may also restrict fuel flow, impacting engine performance and contributing to the problem. Furthermore, issues with the idle air control valve can disrupt the engine's idle speed, while a malfunctioning oxygen sensor can negatively affect the air-fuel mixture, resulting in similar symptoms. By understanding these common problems, DIY enthusiasts can take the necessary steps to diagnose and address the rough idle in their E250, ensuring smoother operation and improved performance.

How urgent is it to address the rough idle in my 2015 Mercedes-Benz E250?

Addressing a rough idle in your 2015 Mercedes-Benz E250 is not just a matter of comfort; it is crucial for the overall health of your vehicle. A rough idle can signal serious underlying problems, such as issues with the fuel system, ignition components, or even engine wear. If these symptoms are ignored, they can escalate into more significant and costly repairs, potentially leading to engine failure. Additionally, a rough idle often correlates with decreased fuel efficiency, which can impact your wallet over time. By taking prompt action to diagnose and resolve the issue, you not only enhance your driving experience but also safeguard your vehicle's longevity and performance. Therefore, it is essential to prioritize addressing a rough idle to prevent further complications and ensure your Mercedes-Benz E250 remains in optimal condition.

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