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2017 Audi A6 3.0T Rough Idle and Misfire Codes

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Mike T. · rep 0 · May 22, 4:25 AM · 1 replies · solved · Question

Vehicle: 2017 Audi A6 3.0T Prestige

Hey everyone,

My 2017 Audi A6 3.0T has developed a really rough idle lately, and I've also noticed a slight hesitation under acceleration. The check engine light came on, and when I scanned it, I got multiple misfire codes: P0301 (Cylinder 1 Misfire Detected), P0303 (Cylinder 3 Misfire Detected), and P0300 (Random/Multiple Cylinder Misfire Detected).

The car has about 70,000 miles on it. I'm thinking it could be spark plugs or ignition coils, but I'm not sure where to start. Could it be something else entirely, like fuel injectors or even a PCV valve issue? Any advice on troubleshooting this would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:25 AM

0

ClearTheCode admin answer:

Experiencing a rough idle and multiple misfire codes (P0300, P0301, P0303) on your 2017 Audi A6 3.0T at 70,000 miles points to a common set of issues. The 3.0T engine, while robust, can develop specific problems that lead to these symptoms.

  1. Check Spark Plugs and Ignition Coils: This is the most common culprit for misfires.
    • Spark Plugs: At 70,000 miles, if they haven't been replaced, they are due or overdue. Worn plugs can lead to weak spark.
    • Ignition Coils: Coils can fail individually. You can try swapping coils between a misfiring cylinder and a non-misfiring one to see if the misfire code follows the coil.
  2. Inspect PCV Valve (Crankcase Ventilation Valve): A failing PCV valve is a very common issue on the 3.0T engine. A ruptured diaphragm in the PCV can cause a vacuum leak, leading to unmetered air entering the intake, which results in a rough idle, misfires, and sometimes even a whistling noise. This can also throw lean codes (P0171/P0174) in addition to misfires.
  3. Fuel Injectors: Clogged or failing fuel injectors can cause misfires by not delivering the correct amount of fuel. This is less common than plugs/coils/PCV but still a possibility.
  4. Intake Manifold Flap Actuators: Less common, but issues with the intake manifold runner flaps or their actuators can also cause air distribution problems leading to misfires.

Common Causes:

  • Worn Spark Plugs/Failing Ignition Coils: Primary suspects for misfires.
  • Failed PCV Valve: A significant and common cause of rough idle and misfires on the 3.0T due to vacuum leaks.
  • Carbon Buildup: While less of an issue on the supercharged 3.0T compared to direct-injection-only engines, it can still contribute to reduced airflow and misfires over time.

When to See a Shop: If replacing spark plugs and swapping coils doesn't resolve the issue, or if you suspect a PCV valve failure (which can be tricky to diagnose without specialized tools), it's best to take your A6 to an Audi specialist. They can perform a smoke test for vacuum leaks, check fuel pressure, and conduct a comprehensive diagnostic scan to pinpoint the exact cause of the misfires.

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