2015 Audi S5 Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2015 Audi S5 and How to Restore Smooth Performance

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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 2015 Audi S5 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 Audi S5 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 Audi S5?

When faced with a rough idle in your 2015 Audi S5, it's essential to adopt a systematic diagnostic approach to effectively identify the root cause. Begin by checking for fault codes using a diagnostic scanner, as these codes can reveal specific issues 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 dirt and debris to maintain proper airflow. Additionally, examine the vacuum lines for any leaks, as these can disrupt the air-fuel mixture and lead to idle problems. Don't overlook the fuel system; check the fuel filter and injectors for clogs or malfunctions that could affect engine operation. Finally, inspect the throttle body for carbon buildup, as cleaning it can often enhance idle quality. By following these steps, you can effectively diagnose and address the rough idle issue in your Audi S5, ensuring a smoother driving experience.

What are the common problems that could cause a rough idle in a 2015 Audi S5?

When dealing with a rough idle in your 2015 Audi S5, it's essential to understand the common problems that could be at play. 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 in the intake system can create an incorrect air-fuel ratio, exacerbating the rough idle issue. Worn-out 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 fuel injectors, whether due to clogging or malfunction, can disrupt fuel delivery to the engine cylinders, resulting in an uneven idle. Lastly, a faulty oxygen sensor can misread the air-fuel mixture, causing further complications. By identifying and addressing these common issues, you can effectively restore smooth idling to your Audi S5, ensuring optimal performance and driving experience.

How urgent is it to address the rough idle in a 2015 Audi S5?

Addressing a rough idle in your 2015 Audi S5 is not just a matter of comfort; it is crucial for the vehicle's overall health and performance. A rough idle can indicate underlying issues within the engine, such as problems with the fuel or ignition systems, or even faulty sensors. Ignoring these symptoms can lead to decreased fuel efficiency and poor performance, which may escalate into more severe engine damage over time. Moreover, a rough idle can sometimes signal serious problems that could worsen if left unattended, potentially compromising your vehicle's safety. Regular maintenance and timely repairs are essential to prevent these complications, ensuring that your Audi S5 operates smoothly and efficiently. Therefore, it is imperative to address any rough idle issues promptly to safeguard your vehicle's longevity and performance.

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