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Rough Idle & Misfire on 2017 Audi A5 Coupe - P0301 Code

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Mike T. · rep 0 · May 26, 3:44 AM · 1 replies · solved · Question

Vehicle: 2017 Audi A5 Coupe Prestige

Hi A5 owners,

My 2017 Audi A5 Coupe Prestige (2.0 TFSI) has recently developed a really rough idle, especially when the engine is cold or at stop lights. The car shakes noticeably, and I can feel a slight loss of power when accelerating from a stop. The check engine light came on, and when I scanned it, I got a P0301 code, indicating a misfire on cylinder 1.

I'm wondering if this is a common issue for this engine in the A5? What should I be looking at first? Spark plugs, ignition coils, or something more serious like an injector problem? Any guidance on troubleshooting this would be incredibly helpful.

Thanks in advance!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 26, 3:44 AM

0

ClearTheCode admin answer:

A P0301 code (Cylinder 1 Misfire Detected) on your 2017 Audi A5 Coupe Prestige indicates that the engine's computer has detected an issue with the combustion process in cylinder 1. This is a common issue on direct-injection engines like the 2.0 TFSI and can be caused by several factors.

Here's a systematic approach to diagnose and potentially resolve the issue:

  1. Check Spark Plugs:
    • Action: Remove and inspect the spark plug in cylinder 1. Look for signs of wear, fouling (oil, carbon, fuel), or damage to the electrode. It's often a good idea to swap the spark plug from cylinder 1 with one from another cylinder (e.g., cylinder 2) and see if the misfire code follows the plug (P0302). If it does, replace all spark plugs as a set.
    • Cause: Worn or fouled spark plugs are a very common cause of misfires.
  2. Inspect Ignition Coils:
    • Action: Similar to spark plugs, swap the ignition coil from cylinder 1 with one from another cylinder. Clear the code and drive the car. If the misfire shifts to the new cylinder (e.g., P0302 appears), then the coil from cylinder 1 is faulty and needs replacement. Consider replacing all coils, especially if they are original.
    • Cause: Faulty ignition coils are a frequent culprit, failing to provide adequate spark.
  3. Fuel Injector Test:
    • Action: If spark plugs and coils are ruled out, the issue might be with the fuel injector for cylinder 1. This requires more advanced diagnostics, often involving measuring fuel pressure, injector resistance, or even removing the injector for testing/cleaning.
    • Cause: Clogged or failing fuel injectors can lead to insufficient fuel delivery for proper combustion.
  4. Vacuum Leaks/PCV System:
    • Action: Inspect vacuum lines around the intake manifold and the PCV (Positive Crankcase Ventilation) valve for cracks or leaks. A smoke test can help identify elusive leaks.
    • Cause: Unmetered air entering the engine can disrupt the air-fuel mixture, leading to misfires.

When to See a Shop:

  • If you've performed the spark plug and coil swaps and the misfire persists or doesn't move.
  • If you suspect a fuel injector issue, as specialized tools are often needed.
  • If you hear unusual noises from the engine or experience significant power loss.
  • An Audi specialist can perform a comprehensive diagnostic scan (VCDS/ODIS) to check for other related fault codes, live data readings (e.g., fuel trims, misfire counters), and compression tests to rule out internal engine issues.
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