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Rough Idle and Misfire on my 2018 XC60 T5 - Check Engine Light On

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Mike T. · rep 0 · May 24, 2:54 PM · 1 replies · solved · Question

Vehicle: 2018 Volvo XC60 T5 Momentum

Hey everyone,

I'm having some trouble with my 2018 Volvo XC60 T5, specifically the Momentum trim. Lately, I've noticed a really rough idle, especially when starting it up cold. It feels like the engine is shaking more than usual, and sometimes it struggles a bit to get going.

Yesterday, the check engine light came on, and the car felt like it was hesitating under acceleration. I'm worried it might be a misfire, but I'm not sure where to start troubleshooting. Has anyone experienced something similar with their T5 engine from this generation?

Any advice or common culprits I should look into before taking it to the dealer would be greatly appreciated. Thanks!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 2:54 PM

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ClearTheCode admin answer:

It sounds like you're definitely dealing with an engine misfire, which is a common issue that can manifest as a rough idle and hesitation. The check engine light confirms that the car's computer has detected a fault. Here’s what you should consider:

  1. Check for OBD-II Codes: The first and most crucial step is to get the diagnostic trouble codes (DTCs) read. You can do this at most auto parts stores for free, or with your own OBD-II scanner. Look for codes in the P030x series (e.g., P0301, P0302, P0303, P0304), where the last digit indicates the cylinder with the misfire. This will pinpoint the problematic cylinder.

  2. Common Causes for Misfires in T5 Engines:

    • Spark Plugs: Worn or fouled spark plugs are a frequent cause of misfires. If they haven't been replaced according to your service schedule (typically around 60,000 miles), they're a prime suspect.
    • Ignition Coils: A failing ignition coil for a specific cylinder will prevent the spark plug from firing correctly. If you get a P030x code, swapping the coil with an adjacent cylinder's coil and rechecking for the code can help diagnose if the coil is bad (if the misfire moves to the new cylinder).
    • Fuel Injectors: A clogged or faulty fuel injector can lead to an improper fuel-air mixture, causing a misfire. This is less common than plugs or coils but still possible.
    • Vacuum Leaks: Leaks in the intake system can introduce unmetered air, leaning out the mixture and causing misfires, especially at idle.
    • Engine Compression: In rarer cases, low compression in a cylinder due to valve issues or piston ring wear can cause a misfire. This requires more in-depth diagnostics.

  3. When to See a Shop:

    • Immediately if the check engine light is flashing. A flashing light indicates a severe misfire that could be damaging your catalytic converter due to unburnt fuel entering the exhaust.
    • If you've checked the basic components (plugs, coils) and the issue persists.
    • If you're uncomfortable performing diagnostics yourself.

Addressing misfires promptly is important to maintain engine health and fuel efficiency. Start with the OBD-II codes; they are your best guide.

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