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2020 TTS Misfires & Rough Idle - P0300, P0301, P0302 - Spark Plugs/Coils?

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Mike T. · rep 0 · May 25, 3:15 AM · 1 replies · solved · Question

Vehicle: 2020 Audi TTS Roadster

Hi all, I'm having some issues with my 2020 Audi TTS Roadster, 2.0T engine, which just hit 45,000 miles. Recently, I've noticed a rough idle, especially when starting cold, and a slight hesitation under acceleration. The Check Engine Light came on and started blinking during a drive, then stayed solid. I scanned it with my OBDeleven, and I'm getting multiple misfire codes: P0300 (Random/Multiple Cylinder Misfire Detected), P0301 (Cylinder 1 Misfire), and P0302 (Cylinder 2 Misfire).

Given the mileage, I'm thinking it might be time for spark plugs, and perhaps ignition coils too. Is 45k miles a typical interval for these on the TTS? What's the best approach for diagnosing if it's plugs, coils, or something else? I'm hoping to do this myself if it's straightforward enough.

Any advice from fellow TTS owners would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:15 AM

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ClearTheCode admin answer:

Your symptoms of rough idle, hesitation, and especially the P0300, P0301, P0302 misfire codes on your 2020 Audi TTS at 45,000 miles are very strong indicators that you're due for spark plug and potentially ignition coil replacement. Audi's recommended spark plug interval for these high-performance 2.0T engines is often around 40,000-60,000 miles, so you're right in that window.

Causes of Misfires:

  1. Worn Spark Plugs: Over time, the electrodes on spark plugs erode, increasing the gap and requiring more voltage to fire, leading to weak or inconsistent sparks.
  2. Failing Ignition Coils: Ignition coils can degrade internally, leading to intermittent or complete failure to produce a strong spark. Heat and age are common culprits.
  3. Fuel Delivery Issues: Less common, but clogged fuel injectors or low fuel pressure can also cause misfires.
  4. Compression Issues: (Least likely given your mileage and specific codes) Low compression in a cylinder can also cause misfires.

Recommended Steps for Diagnosis & Repair:

  1. Swap Coils: A common diagnostic step is to swap the ignition coils from the misfiring cylinders (1 and 2) with coils from non-misfiring cylinders (3 and 4). Clear the codes, drive the car, and re-scan. If the misfire codes follow the coils (e.g., now you get P0303, P0304), then the coils are the issue.
  2. Inspect Spark Plugs: If swapping coils doesn't shift the misfire, remove the spark plugs from cylinders 1 and 2 (and ideally all of them). Inspect them for wear, fouling, or damage. Gapping issues can also be a factor, though modern plugs are usually pre-gapped.
  3. Replace Spark Plugs: It's generally good practice to replace all spark plugs at your mileage, especially on a performance engine. Use OEM (NGK, Bosch, etc.) or equivalent performance-oriented plugs specified for your engine.
  4. Replace Coils (if needed): If your diagnosis points to coils, it's often wise to replace all four at once, as they tend to fail around the same time. Many enthusiasts upgrade to 'red top' R8/RS3 coils for improved performance and longevity, though standard OEM coils are perfectly fine.
  5. Torque Specs: Ensure spark plugs are torqued correctly to prevent loosening or damage to the cylinder head threads.

When to See a Shop:

  • If, after replacing plugs and coils, the misfires persist or new codes appear, indicating a deeper issue like fuel injectors, carbon buildup (common on direct injection engines), or compression problems.
  • If you're uncomfortable with the DIY process, as incorrect installation can lead to further engine problems.
  • If the CEL is blinking, it indicates a severe misfire that could damage the catalytic converter. Minimize driving until the issue is resolved.
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