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2017 Audi S5 Coupe Rough Idling and Check Engine Light

0

Mike T. · rep 0 · May 26, 3:48 AM · 1 replies · solved · Question

Vehicle: 2017 Audi S5 Coupe Premium Plus

My 2017 Audi S5 Coupe Premium Plus has recently started idling really rough, especially when cold. It feels like the engine is shaking more than usual, and sometimes it even hesitates a bit when I try to accelerate from a stop. This morning, the check engine light came on, which has me pretty worried.

I haven't noticed any significant loss of power, but the car just doesn't feel as smooth as it used to. The fuel economy also seems to have taken a slight hit. I usually keep up with all my regular maintenance, so this is a bit unexpected.

Has anyone experienced similar symptoms with their S5? Could it be something simple like spark plugs, or something more serious? Any ideas on what might be causing this would be a huge help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 26, 3:48 AM

0

ClearTheCode admin answer:

Rough idling and a check engine light on a 2017 Audi S5 can indicate several issues, ranging from minor to more significant. Given your description, it's important to address this promptly.

  1. Retrieve OBD-II Codes: The first and most crucial step is to get the diagnostic trouble codes (DTCs) from the check engine light. You can do this with an OBD-II scanner. Common codes associated with rough idling and hesitation include:
    • P030x (e.g., P0301, P0302, etc.): Misfire detected in cylinder X. This points to ignition system issues.
    • P0171/P0174: System too lean (Bank 1/Bank 2). This could indicate a vacuum leak, faulty PCV valve, or fuel delivery problem.
    • P0420/P0430: Catalyst system efficiency below threshold. While less likely to cause rough idling directly, it can be a secondary symptom if other issues are present.
  2. Inspect Ignition System: If you have misfire codes, check your spark plugs and ignition coils. Worn spark plugs or failing coils are common culprits for rough idling and hesitation.
  3. Check for Vacuum Leaks: A vacuum leak can cause unmetered air to enter the engine, leading to a lean condition and rough idle. Listen for hissing sounds under the hood and inspect vacuum lines.
  4. Examine PCV Valve: The Positive Crankcase Ventilation (PCV) valve system can fail, leading to vacuum leaks or oil consumption, both of which can cause rough idling.

Common Causes:

  • Failing Ignition Coils or Spark Plugs: These are very common wear items that directly affect engine combustion.
  • Vacuum Leaks: Cracked hoses or gaskets can introduce extra air, disrupting the air-fuel mixture.
  • Faulty PCV Valve: A common failure point that can lead to rough idle and lean codes.
  • Fuel System Issues: Clogged fuel injectors or a failing fuel pump can also cause similar symptoms, though less common than ignition problems.

When to See a Shop: If you retrieve misfire codes or lean codes, and a visual inspection doesn't reveal an obvious issue, or if replacing basic components like spark plugs doesn't help, it's best to take your S5 to a qualified mechanic or Audi dealership. They have advanced diagnostic equipment to accurately pinpoint the root cause, especially for issues like fuel system problems or more complex sensor failures.

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