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2020 XC90 T8 Rough Idle and Misfire - Check Engine Light On

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David L. · rep 0 · May 25, 3:53 AM · 1 replies · solved · Question

Vehicle: 2020 Volvo XC90 T8 Recharge

Hello everyone,

I'm reaching out about an issue with my 2020 Volvo XC90 T8 Recharge, which has just over 50,000 miles. For the past week, the engine has developed a noticeable rough idle, especially when running on gasoline (not electric). It feels like it's shaking more than usual, and there's a distinct misfire sensation.

The check engine light came on and has stayed on. I used an OBD scanner, and it's showing multiple misfire codes: P0301 (Cylinder 1 Misfire), P0302 (Cylinder 2 Misfire), and P0300 (Random/Multiple Cylinder Misfire Detected). Given it's a hybrid, I'm concerned about how this might affect both the gas engine and the electric system.

Has anyone experienced similar misfire issues with their T8 engine? What were the common causes, especially considering it's a newer model with relatively low mileage? Any specific things I should look into before taking it to the dealer?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:53 AM

0

ClearTheCode admin answer:

Multiple misfire codes (P0300, P0301, P0302) on your 2020 Volvo XC90 T8 indicate that the engine is not burning fuel efficiently in those cylinders. Given it's a T8, the complexity of the hybrid system adds a layer to diagnostics, but the core misfire causes are generally similar to conventional gasoline engines.

Here are the most common causes for misfires in a modern Volvo T8 engine:

  1. Ignition System Components:
    • Spark Plugs: These are a primary suspect. Worn or fouled spark plugs are a very common cause of misfires. While 50,000 miles might be a bit early for some plugs, high-performance engines like the T8 can be harder on them.
    • Ignition Coils: A failing ignition coil for cylinder 1 and 2 would directly cause P0301 and P0302. You might try swapping coils between cylinders to see if the misfire moves.
  2. Fuel System Issues:
    • Fuel Injectors: Clogged or faulty fuel injectors for cylinders 1 and 2 could lead to insufficient fuel delivery, causing misfires. Fuel quality can sometimes contribute to this.
    • Low Fuel Pressure: A failing fuel pump or regulator could cause overall low fuel pressure, leading to misfires across multiple cylinders (P0300).
  3. Compression Issues: While less likely for a 2020 model, a loss of compression in cylinders 1 and 2 (due to valve issues, head gasket, or piston rings) would cause misfires. This usually presents with other symptoms like smoke or coolant loss.
  4. Vacuum Leaks: Unmetered air entering the intake manifold can lean out the air-fuel mixture, leading to misfires. This might affect multiple cylinders.

When to See a Shop:

  • Immediately: If the engine is shaking violently, you notice a strong smell of raw fuel from the exhaust, or if the check engine light is flashing (indicating severe misfires that can damage the catalytic converter). Driving with persistent misfires can lead to costly catalytic converter damage.
  • Soon: A qualified Volvo technician should perform a comprehensive diagnostic. They can check spark plugs, ignition coils, test fuel pressure, and perform injector tests. Given it's a T8, they can also ensure the hybrid system isn't indirectly contributing to the issue, though misfires are typically a combustion engine problem. They have specialized diagnostic tools to pinpoint the exact cause efficiently.
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