Mercedes-Benz GLE350 Has Rough Idle

Diagnosing the Causes of Rough Idle in Your Mercedes-Benz GLE350 and How to Resolve Them

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Reviewed by
Bo Fader
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 Mercedes-Benz GLE350 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 Mercedes-Benz GLE350 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.

Brake caliper failure occurs in two different ways, and they create different symptoms.

The caliper can become stuck, in which case it won't release the brake pads. The seized caliper will cause the vehicle to brake constantly on one side, forcing the car to move toward that side. This pulling will be accompanied by a strong odor from one wheel.

Another way calipers fail is by leaking. If the caliper leaks, the brake pedal will feel too easy to push, and will sink all the way to the floor when held. Braking will become less effective the longer this goes on. There may also be brake fluid leaking onto the wheel.

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.

Brake rotors are mainly maintenance free, but when they have been subjected to abnormally hard use, the heat they absorb can cause the metal to turn blue, and cracking to occur. When this occurs, customers often specify they have lost braking power, or the vehicle's brakes are making noise. There may be no symptoms at all related to changing the brake rotors, since it is recommended to change brake rotors on most modern vehicles when performing a standard brake service.

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.

Troubleshooting Rough Idle in a Mercedes-Benz GLE350

When faced with a rough idle in your Mercedes-Benz GLE350, it's essential to adopt a methodical diagnostic approach. Begin by inspecting for vacuum leaks, as these can significantly disrupt the air-fuel mixture, leading to unstable idling. A simple visual check around hoses and connections can often reveal any obvious issues. Next, turn your attention to the spark plugs; worn or damaged plugs can cause misfires, which are a common culprit of rough idling. If the spark plugs appear to be in good condition, proceed to test the ignition coil, as a malfunction here can also contribute to the problem. Additionally, keep an eye on the check engine light; if it illuminates, it may indicate misfires that require further investigation. Lastly, consider the behavior of the start-stop system, as irregularities here can lead to jerking or rough idling when the vehicle is stationary. By following this structured approach, you can effectively diagnose and address the rough idle issue in your GLE350, ensuring a smoother driving experience.

Troubleshooting Rough Idle Issues in a Mercedes-Benz GLE350

When dealing with rough idle issues in your Mercedes-Benz GLE350, it's essential to understand the common problems that may be at play. One frequent culprit is a vacuum leak, which can disrupt the delicate balance of the air-fuel mixture, leading to an unstable idle. Additionally, worn or fouled spark plugs can cause misfires, contributing to the roughness you experience. Ignition coil problems are another potential source of trouble, as they directly impact the ignition process and can result in uneven engine performance. To effectively diagnose these issues, start by using a scanner to check for any fault codes that may provide clues about the underlying problem. It's also wise to inspect the secondary air pump for any signs of backfires or misses, as these can trigger fault codes as well. Cleaning the idle control valve and adjusting the mixture control screw can help optimize your engine's idle speed. Lastly, don't overlook the importance of checking the coil pack and fuel system, as these components can also play a significant role in maintaining a smooth idle. By systematically addressing these common problems, you can restore your GLE350's performance and enjoy a smoother driving experience.

Why is a Rough Idle in a Mercedes-Benz GLE350 a Cause for Concern?

A rough idle in your Mercedes-Benz GLE350 is not just an annoyance; it can signal serious underlying issues that require immediate attention. Ignoring symptoms like engine misfires can lead to a shaky driving experience, which not only diminishes comfort but also poses safety risks. Problems such as vacuum leaks or faulty spark plugs can escalate if left unaddressed, potentially resulting in costly repairs and further engine damage. The vibrations associated with a rough idle can affect critical components, compromising the vehicle's overall performance and safety. Therefore, it is crucial to diagnose and resolve these issues promptly to ensure your vehicle operates smoothly and efficiently, safeguarding both your investment and your driving experience.

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Mercedes-Benz GLE350 Rough Idle Causes & Repairs | RepairPal