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2018 XC60 T5 Rough Idle and Check Engine Light - Misfire?

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Mark S. · rep 0 · May 22, 5:13 AM · 1 replies · solved · Question

Vehicle: 2018 Volvo XC60 T5 Momentum

Hey everyone,

I'm having an issue with my 2018 Volvo XC60 T5 Momentum. Lately, I've noticed a really rough idle, especially when the engine is cold or at stop lights. It feels like the car is shaking more than it should.

Yesterday, the check engine light came on. I haven't had a chance to get it scanned yet, but I'm worried it might be something serious. The car also seems to hesitate slightly under light acceleration sometimes.

Has anyone experienced something similar with their T5 engine? What should I be looking for? Any advice on common culprits for this model year would be greatly appreciated before I take it to the dealer.

Thanks!

✓ 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 XC60 T5 is experiencing symptoms consistent with an engine misfire or a lean fuel condition, which are common causes for a rough idle and a check engine light. The hesitation under acceleration further supports this.

Common Causes for Rough Idle/Misfire in Volvo T5 Engines (2016-2026):

  1. Ignition System Issues: Worn spark plugs, failing ignition coils, or damaged spark plug wires (less common on modern engines) are frequent culprits. A single faulty coil can cause a specific cylinder misfire.
  2. Fuel System Problems: Clogged fuel injectors, a failing fuel pump, or a dirty fuel filter can lead to insufficient fuel delivery to one or more cylinders.
  3. Vacuum Leaks: Leaks in the intake manifold, PCV system hoses, or other vacuum lines can introduce unmetered air, causing a lean condition and rough running.
  4. PCV System: Volvo's Drive-E engines can sometimes develop issues with the PCV (Positive Crankcase Ventilation) system, leading to vacuum leaks or excessive crankcase pressure, which impacts engine performance.
  5. Sensor Malfunctions: A faulty Mass Air Flow (MAF) sensor or Oxygen (O2) sensor can send incorrect data to the engine control unit (ECU), leading to improper fuel-air mixture calculations.

Diagnostics & Next Steps:

  1. Scan for Diagnostic Trouble Codes (DTCs): This is the most crucial first step. Common codes you might see include:
    • P030X: (e.g., P0301 for Cylinder 1 Misfire, P0302 for Cylinder 2, etc.) indicating a specific cylinder misfire.
    • P0171: System Too Lean (Bank 1), suggesting a vacuum leak or fuel delivery issue.
    • P0420/P0430: Catalyst System Efficiency Below Threshold (Bank 1/2), which can sometimes be triggered by prolonged misfires.
  2. Inspect Spark Plugs and Ignition Coils: If a misfire code is present, visually inspect the spark plug and coil for that cylinder. Look for signs of wear, oil fouling, or cracks.
  3. Check for Vacuum Leaks: Listen for hissing sounds around the engine bay, especially near the intake manifold and PCV system. A smoke test can definitively identify small leaks.

When to See a Shop:

  • Flashing Check Engine Light: If the CEL is flashing, it indicates a severe misfire that could be damaging your catalytic converter. Drive as little as possible and get it to a shop immediately.
  • Persistent Symptoms: If you've scanned for codes and performed basic visual checks without identifying the issue, or if the problem persists after addressing a known cause, professional diagnosis is recommended.
  • Loss of Power or Unusual Noises: Any significant loss of power, stalling, or new engine noises warrant immediate professional attention to prevent further damage.
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