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2018 S60 T5 Rough Idle & Misfire - "Reduced Engine Performance"

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Emily N. · rep 0 · May 22, 5:13 AM · 1 replies · solved · Question

Vehicle: 2018 Volvo S60 T5

Hey everyone, hoping for some advice here. My 2018 Volvo S60 T5, with about 75k miles, has recently started acting up. I'm experiencing a really rough idle, especially when the engine is cold, and it feels like it's misfiring occasionally. The 'Reduced Engine Performance' message has popped up on the dash a couple of times, usually when I'm accelerating moderately.

I've noticed a slight hesitation when I try to speed up, and the fuel economy seems to have taken a hit. No check engine light is currently on, but it did flash briefly once or twice. I'm a bit worried about driving it like this.

Has anyone else with a similar Volvo S60 T5 experienced these symptoms? What could be causing this, and what should I check first? Any common issues with these engines around this mileage?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:13 AM

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ClearTheCode admin answer:

It sounds like your 2018 Volvo S60 T5 is experiencing classic symptoms of an engine misfire, which can trigger the 'Reduced Engine Performance' message. Even if the Check Engine Light isn't constantly on, brief flashes indicate a significant misfire event.

Here are common causes and steps:

  1. Check for Diagnostic Trouble Codes (DTCs): Get the car scanned for codes first. A pending or stored history code (like P030x for a specific cylinder misfire, e.g., P0301) will provide a crucial starting point. Many auto parts stores offer free code reading.

  2. Ignition System Components:

    • Spark Plugs: Worn or fouled spark plugs are a very common cause of misfires. If not recently replaced (typically every 60k-80k miles), they're a prime suspect.
    • Ignition Coils: A failing ignition coil on one cylinder can lead to intermittent or constant misfires. These degrade over time with heat cycles.

  3. Fuel System Issues:

    • Fuel Injectors: A clogged or faulty fuel injector can cause a cylinder to run lean or rich, leading to a misfire.
    • Fuel Pressure: Less common, but low fuel pressure could affect overall engine performance.

  4. Vacuum Leaks: An unmetered air leak in the intake system (e.g., a cracked hose, faulty PCV valve, or intake manifold gasket) can lean out the air-fuel mixture, causing rough idle and misfires. Volvo T5 engines can be sensitive to PCV system integrity.

When to See a Shop: If you've pulled codes and they point to a specific cylinder (e.g., P0301), you might try swapping components like spark plugs or ignition coils between cylinders to see if the misfire moves. However, if the issue persists, or if you're not comfortable with DIY diagnostics, take your Volvo to a qualified mechanic or a Volvo specialist. Continued driving with a significant misfire can damage the catalytic converter due to unburnt fuel entering the exhaust system. A professional can perform comprehensive diagnostics to pinpoint the exact cause.

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