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2017 Audi A5 Sportback Check Engine Light & Rough Idle

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Mike T. · rep 0 · May 26, 3:53 AM · 1 replies · solved · Question

Vehicle: 2017 Audi A5 Sportback 2.0T

My 2017 Audi A5 Sportback, 2.0T engine, just threw a check engine light, and it's been running pretty rough at idle. When I'm driving, it feels a bit sluggish, like it's lost some power, and the exhaust note sounds a little off. It's got about 60,000 miles on it.

I pulled the code with a basic OBD-II scanner, and it's showing P0301, which indicates a misfire on cylinder 1. I'm wondering if it's just a bad spark plug or ignition coil, or if it could be something more serious like a fuel injector or even carbon buildup. I've heard carbon buildup can be an issue with these direct-injection engines.

Any thoughts on what might be the most likely culprit for a P0301 on a 2017 A5? What's the best way to troubleshoot this without just throwing parts at it?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 26, 3:53 AM

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ClearTheCode admin answer:

A P0301 code on your 2017 Audi A5 Sportback's 2.0T engine, indicating a misfire on cylinder 1, is a common issue with direct-injection engines and can be caused by several factors. It's good that you've already pulled the code.

  1. Swap Ignition Coil: The easiest diagnostic step is to swap the ignition coil from cylinder 1 to a different cylinder (e.g., cylinder 2). Clear the code and drive the car. If the misfire moves to cylinder 2 (P0302), you've identified a faulty ignition coil. This is a common failure point.
  2. Swap Spark Plug: If swapping the coil doesn't move the misfire, try swapping the spark plug from cylinder 1 to another cylinder. A fouled or worn spark plug can cause misfires. Ensure you're using the correct OEM-spec spark plugs for your engine.
  3. Check Fuel Injector: If the misfire remains on cylinder 1 after swapping coils and plugs, the fuel injector for cylinder 1 could be faulty (clogged or failing). This requires more specialized testing, often involving removing the injector for inspection and flow testing.
  4. Inspect for Carbon Buildup: Direct-injection engines are prone to carbon buildup on the intake valves, which can restrict airflow and cause misfires. While 60,000 miles is when it often starts to become noticeable, it might not be the primary cause of a single cylinder misfire. However, it's worth considering if other common causes are ruled out.
  5. Compression Test: A compression test on cylinder 1 can rule out internal engine issues like a bad valve or piston ring, which would be a more serious and less common cause.

When to See a Shop: If swapping coils and plugs doesn't resolve the P0301 code, or if you suspect a fuel injector or carbon buildup, it's best to take your A5 to an Audi specialist. They have the proper diagnostic equipment (such as a borescope to inspect intake valves for carbon buildup, and tools to test fuel injector performance) and expertise to accurately diagnose the root cause. Driving with a persistent misfire can lead to catalytic converter damage and further engine issues, so prompt repair is important.

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