2013 Mercedes-Benz E400 Has Rough Idle

Resolve Rough Idle Issues in Your 2013 Mercedes-Benz E400 for a Smoother Ride

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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 2013 Mercedes-Benz E400 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 2013 Mercedes-Benz E400 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 2013 Mercedes-Benz E400?

When diagnosing a rough idle in a 2013 Mercedes-Benz E400, it's essential to adopt a systematic diagnostic approach that prioritizes simpler checks before delving into more complex issues. Start by using a diagnostic scanner to check for any fault codes, as these can quickly point you to specific problems within the vehicle's systems. Next, inspect the spark plugs for wear or fouling, as these components play a crucial role in engine performance. A clean air filter is also vital; ensure it is free from clogs that could restrict airflow. Following this, examine the fuel system, including the fuel filter and injectors, to confirm that fuel delivery is optimal. Don't overlook the vacuum hoses; any leaks or damage here can significantly impact engine idle. Additionally, inspect the throttle body for carbon buildup, which can obstruct airflow and affect idle quality. Finally, consider performing a smoke test to identify any vacuum leaks in the intake system. By following this structured approach, you can effectively diagnose and resolve the rough idle issue in your E400, ensuring a smoother driving experience.

What are the common problems that could cause a rough idle in a 2013 Mercedes-Benz E400?

When diagnosing a rough idle in your 2013 Mercedes-Benz E400, 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 air and fuel entering the engine. Additionally, vacuum leaks can create an improper air-fuel mixture, leading to instability during idle. It's also crucial to inspect the spark plugs and ignition coils, as worn components can cause misfires that contribute to a rough idle. A clogged fuel filter may restrict fuel flow, further exacerbating the issue. Furthermore, the idle air control valve plays a significant role in maintaining a steady idle speed, and any malfunction here can lead to erratic engine behavior. Lastly, a malfunctioning throttle body can hinder air intake, resulting in an uneven idle. By systematically checking these components, you can effectively troubleshoot and resolve the rough idle issue, ensuring your E400 runs smoothly.

How urgent is it to address the rough idle in a 2013 Mercedes-Benz E400?

When dealing with a rough idle in your 2013 Mercedes-Benz E400, understanding the urgency of the situation is crucial. A rough idle can indicate underlying issues that may compromise the safety and performance of your vehicle. For instance, if the rough idle is linked to engine misfires or fuel delivery problems, it could lead to more severe engine damage if left unaddressed. Additionally, a rough idle often results in decreased fuel efficiency, which not only affects your wallet but also contributes to higher emissions, potentially causing your vehicle to fail emissions tests. Therefore, it is essential to prioritize diagnosing the issue promptly. While it may not always require immediate action, considering the potential safety risks and long-term costs associated with neglecting the problem can help you make an informed decision. Consulting a professional mechanic can provide clarity on the urgency of the situation, ensuring that your vehicle remains safe and efficient on the road.

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Diagnose Rough Idle Issues in 2013 Mercedes-Benz E400