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2018 XC60 T5 Rough Idle, Stalling, and P0171 Code

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Nicole W. · rep 0 · May 22, 5:13 AM · 1 replies · solved · Question

Vehicle: 2018 Volvo XC60 T5 Momentum

Hey everyone,

I'm having some frustrating issues with my 2018 Volvo XC60 T5 Momentum. Lately, it's developed a really rough idle, especially when I'm stopped at a light or in traffic. Sometimes, it even feels like it's going to stall, and it has actually stalled a couple of times when coming to a stop.

The check engine light came on, and when I scanned it, I got a P0171 code: System Too Lean (Bank 1). I've checked the gas cap, but that doesn't seem to be the issue. The car has about 75,000 miles on it.

Has anyone else experienced this with their T5 engine? What should I be looking for? Any advice on common culprits for this code and symptoms in these Volvos would be greatly appreciated before I take it to the dealer.

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

Hello Sarah,

The P0171 code (System Too Lean Bank 1) on your 2018 Volvo XC60 T5, combined with rough idle and stalling, points to your engine receiving too much air or not enough fuel. This is a relatively common diagnostic trouble code that can stem from several sources in modern direct-injection engines like Volvo's Drive-E T5.

Here are the most common causes and steps to consider:

  1. Vacuum Leaks: This is a very frequent cause. Check all vacuum lines, intake manifold gaskets, and the PCV (Positive Crankcase Ventilation) system for any cracks, loose connections, or failed components. A failing PCV diaphragm can often lead to a lean condition and rough idle.
  2. Mass Air Flow (MAF) Sensor: A dirty or failing MAF sensor can send incorrect air intake readings to the engine control unit (ECU), leading to an improper fuel-air mixture. Cleaning it with a specialized MAF cleaner can sometimes resolve the issue, but replacement may be necessary.
  3. Oxygen Sensors: A faulty upstream (pre-catalytic converter) oxygen sensor can provide inaccurate data to the ECU, causing it to lean out the fuel mixture. While less common to be the primary cause of P0171 without other codes, it's worth considering.
  4. Fuel Delivery Issues:
    • Clogged Fuel Injectors: Dirty or partially clogged fuel injectors can restrict fuel flow to one or more cylinders, leading to a lean condition. Fuel system cleaner might help, but professional cleaning or replacement could be needed.
    • Weak Fuel Pump: A failing fuel pump or a clogged fuel filter (less common on newer Volvos with lifetime filters) could reduce fuel pressure.

When to see a shop: If you're not comfortable performing these checks yourself, or if basic troubleshooting (like checking visible vacuum lines or cleaning the MAF) doesn't resolve the issue, it's crucial to take your XC60 to a qualified Volvo specialist or dealership. They have specialized diagnostic tools to pinpoint the exact cause, especially for vacuum leaks that might be internal to the PCV system or for precise fuel pressure testing. Continuing to drive with a lean condition can potentially lead to long-term engine damage, including catalytic converter failure.

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