2023 Audi S4 Has Rough Idle

Troubleshooting Causes of Rough Idle in Your 2023 Audi S4 and How to Resolve Them

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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 2023 Audi S4 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 2023 Audi S4 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.

What are the steps to diagnose a rough idle in a 2023 Audi S4?

To effectively diagnose a rough idle in your 2023 Audi S4, start by checking for fault codes using a diagnostic scanner. This initial step can reveal underlying issues that may not be immediately visible. Next, inspect the spark plugs for wear or fouling, as these can lead to misfires and contribute to a rough idle. Following this, examine the ignition system, including ignition coils and wires, to ensure they are functioning correctly. A malfunction here can significantly impact engine performance. Afterward, turn your attention to the air intake system; check the air filter, mass airflow sensor, and throttle body for any obstructions that could hinder airflow. Additionally, inspect the fuel system by ensuring the fuel filter is clean and the fuel injectors are operating properly, as fuel delivery issues can also cause rough idling. Finally, check the vacuum hoses for any leaks or cracks, as these can disrupt the air-fuel mixture and exacerbate idle problems. By systematically addressing these areas, you can effectively diagnose and resolve the rough idle in your Audi S4, ensuring optimal performance.

What are the common problems that could cause a rough idle in a 2023 Audi S4?

When dealing with a rough idle in your 2023 Audi S4, it's crucial to understand the common problems that could be at play. One of the primary culprits is a dirty or clogged air filter, which can significantly restrict airflow to the engine, leading to performance issues. Additionally, faulty spark plugs may cause misfiring, further contributing to an uneven idle. Vacuum leaks are another potential issue, as they can disrupt the delicate air-fuel mixture necessary for smooth engine operation. Problems within the fuel system, such as a clogged fuel filter or a malfunctioning fuel pump, can also impact engine performance and result in a rough idle. Furthermore, a malfunctioning mass airflow sensor can throw off the air-fuel balance, exacerbating the problem. Don't overlook the throttle body; if it's dirty or not functioning correctly, it can hinder airflow to the engine. Lastly, engine misfires, which can stem from various ignition or fuel delivery issues, can lead to a rough idle as well. Addressing these issues promptly is essential for maintaining the optimal performance of your Audi S4, and if you're unsure, consulting a qualified mechanic can help diagnose and resolve the underlying problems effectively.

How urgent is it to address the rough idle in my 2023 Audi S4?

Addressing a rough idle in your 2023 Audi S4 is not just a matter of comfort; it is crucial for the overall health of your vehicle. A rough idle can indicate serious underlying issues such as faulty spark plugs, a clogged fuel filter, or a malfunctioning oxygen sensor. Ignoring these symptoms can lead to decreased fuel efficiency and engine misfires, which may escalate into more severe engine damage over time. For DIY enthusiasts, it’s essential to recognize that timely maintenance can save you from costly repairs down the line. Regularly inspecting components like spark plugs and fuel filters can help you catch problems early. If you notice a rough idle, consider conducting a thorough inspection or consulting a qualified mechanic to diagnose the issue. Taking prompt action not only enhances your driving experience but also ensures the longevity and performance of your Audi S4.

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