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2017 Volvo S90 T6 - Misfire on Cylinder 3, P0303 Code

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Kevin B. · rep 0 · May 22, 5:17 AM · 1 replies · solved · Question

Vehicle: 2017 Volvo S90 T6 Inscription

Hey guys,

My 2017 Volvo S90 T6 Inscription, with about 70,000 miles, recently started running a bit rough, especially at idle. The Check Engine Light came on, and when I scanned it, I got a P0303 code, indicating a misfire on Cylinder 3.

I'm thinking it might be spark plugs or an ignition coil. I haven't changed the plugs since I bought the car used at 40k miles. What's the recommended interval for spark plugs on these T6 engines? Should I just replace all the plugs and coils, or try to diagnose Cylinder 3 specifically?

Any advice on troubleshooting this would be great!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:17 AM

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ClearTheCode admin answer:

A P0303 code on your 2017 Volvo S90 T6 indicates a misfire detected in cylinder #3. This is a common issue and can often be resolved with routine maintenance or a targeted repair. Here's a breakdown of troubleshooting steps:

  1. Understand the P0303 Code: This code specifically points to cylinder 3. While a general misfire could be many things, focusing on one cylinder helps narrow down the possibilities.
  2. Spark Plugs:
    • Interval: For your T6 engine, Volvo generally recommends spark plug replacement every 60,000 miles or 6 years, whichever comes first. Given your car is at 70,000 miles and you're unsure of the last change, this is a very strong candidate.
    • Action: It's often best practice to replace all spark plugs at once, as they wear similarly. Use genuine Volvo spark plugs or high-quality OEM equivalent iridium plugs (e.g., NGK or Denso) specified for your engine.
  3. Ignition Coils:
    • Diagnosis: To test if the coil is the issue, you can try swapping the ignition coil from cylinder 3 to another cylinder (e.g., cylinder 1). Clear the code, drive the car, and if the misfire code changes to P0301 (misfire on cylinder 1), then the coil is faulty.
    • Action: If the coil is bad, you can replace just the faulty one, though some owners prefer to replace them in sets or all at once for preventative maintenance.
  4. Other Potential Causes (Less Common for P0303, but possible):
    • Fuel Injector: A clogged or faulty fuel injector for cylinder 3 could cause a misfire. This is harder to diagnose without specialized tools.
    • Compression Issue: Low compression in cylinder 3 (due to valve issues, piston rings, etc.) is a more serious mechanical problem. A compression test would be needed.
    • Vacuum Leak: While less likely to be cylinder-specific, a significant vacuum leak could affect engine performance.

When to See a Shop:

  • If replacing spark plugs and swapping coils does not resolve the P0303 code.
  • If you suspect a fuel injector issue or a more serious internal engine problem (e.g., low compression).
  • If you are uncomfortable performing the diagnosis or replacement yourself, especially with the delicate nature of ignition coils and spark plugs.
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