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2017 A4 2.0 TFSI Rough Idle and Misfire Codes

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Mark S. · rep 0 · May 22, 4:25 AM · 1 replies · solved · Question

Vehicle: 2017 Audi A4 Premium Plus

Hey everyone,

I'm having some frustrating issues with my 2017 Audi A4 Premium Plus, 2.0 TFSI engine. Lately, it's developed a really rough idle, especially when cold, and the check engine light came on. I scanned it with my OBD-II reader, and I'm getting P0301 (Cylinder 1 Misfire Detected) and P0300 (Random/Multiple Cylinder Misfire Detected).

I recently had the spark plugs replaced about 5,000 miles ago, thinking that might be the issue, but it hasn't helped. The car feels a bit sluggish under acceleration too. Any ideas on what could be causing this? Could it be ignition coils, or something more serious like carbon buildup?

Thanks for any insights!

✓ Accepted solution

ClearTheCode Admin

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

0

ClearTheCode admin answer:

Rough idle and misfire codes (P0301, P0300) on a 2.0 TFSI engine like in your 2017 Audi A4 are common and can stem from several sources. Given you've recently changed spark plugs, we can likely rule that out as the primary cause, though ensuring they are the correct OEM specification is always a good first check.

Here are the common causes and steps for diagnosis:

  1. Ignition Coils: These are a very frequent culprit for misfires on TFSI engines. Even if one cylinder is misfiring, it's often recommended to replace all four coils, as they tend to fail around the same time. You can try swapping the coil from Cylinder 1 with another cylinder and see if the misfire code follows the coil.
  2. Fuel Injectors: A faulty fuel injector can lead to a lean or rich condition in a cylinder, causing misfires. This is more complex to diagnose without specialized tools but can be indicated by fuel trim values.
  3. Carbon Buildup: Direct injection engines are prone to carbon buildup on the intake valves. This restricts airflow and can cause misfires, especially at idle. This typically requires a walnut blasting service to clean.
  4. PCV Valve (Positive Crankcase Ventilation): A failing PCV valve can cause vacuum leaks, leading to rough idle and misfires. You might hear a whistling sound or notice excessive oil consumption.
  5. Compression Issues: Less common, but low compression in a cylinder due to worn piston rings or valve issues can cause misfires. This requires a compression test.

When to see a shop: If swapping ignition coils doesn't resolve the issue, or if you suspect carbon buildup, fuel injector problems, or PCV valve failure, it's best to take your Audi to a qualified independent Audi specialist or dealership. They have the diagnostic tools (like VCDS or ODIS) to pinpoint the exact cause, perform necessary tests (e.g., fuel pressure, compression, smoke test for vacuum leaks), and perform services like walnut blasting or injector replacement safely and effectively. Continuing to drive with persistent misfires can damage your catalytic converter.

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