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2020 Acadia Rough Idle & Occasional Stall - No CEL Yet

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Kevin B. · rep 0 · May 22, 3:39 AM · 1 replies · solved · Question

Vehicle: 2020 GMC Acadia SLT

My 2020 GMC Acadia SLT (3.6L V6) has developed a really rough idle lately. It feels like it's shaking more than usual when stopped at a light, and a couple of times it's even stalled when coming to a stop.

What's weird is that there's no check engine light on yet. I've checked with a basic scanner, and no codes are stored. The mileage is around 60,000 miles.

Could this be something simple like spark plugs, or something more serious? I'm worried about driving it too much if it's going to keep stalling. Any ideas on what to look for?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:39 AM

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ClearTheCode admin answer:

It's concerning when your 2020 GMC Acadia SLT is experiencing a rough idle and stalling without a Check Engine Light (CEL). This often indicates an intermittent issue or a problem that hasn't yet met the parameters to trigger a diagnostic trouble code. Here are some common areas to investigate:

  1. Ignition System: Worn spark plugs, faulty ignition coils, or bad spark plug wires (less common on modern engines) can cause misfires leading to a rough idle and stalling. Given your mileage, spark plugs are a good starting point.
  2. Fuel System:
    • Clogged Fuel Filter: Restricts fuel flow, especially under load or during deceleration.
    • Weak Fuel Pump: Not delivering adequate fuel pressure.
    • Dirty Fuel Injectors: Can cause an uneven fuel spray pattern, leading to misfires.
  3. Air Intake System:
    • Dirty Throttle Body: Carbon buildup can restrict airflow, especially at idle.
    • Mass Air Flow (MAF) Sensor: A dirty or faulty MAF sensor can send incorrect air readings to the engine computer, affecting fuel-air mixture.
    • Vacuum Leaks: Unmetered air entering the engine can cause a lean condition and rough idle. Listen for hissing sounds.
  4. PCV System: A clogged or faulty PCV valve can cause vacuum issues and affect idle quality.

When to See a Shop:

Since there's no CEL, diagnosing this can be tricky without specialized tools. A professional mechanic can perform a comprehensive diagnostic, including:

  • Live data monitoring of fuel trims, O2 sensor readings, and MAF sensor output.
  • Fuel pressure test.
  • Smoke test for vacuum leaks.
  • Ignition system testing.

It's advisable to have it checked soon, as stalling can be a safety hazard, and continued operation with an undiagnosed issue could lead to more significant engine damage.

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