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2018 LaCrosse - Stalling at Idle and Rough Running

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Mike T. · rep 0 · May 25, 2:44 AM · 1 replies · solved · Question

Vehicle: 2018 Buick LaCrosse Premium

Hi everyone, I'm having a persistent and concerning issue with my 2018 Buick LaCrosse, 3.6L V6 engine, with about 70,000 miles. Lately, it's been stalling randomly when I come to a stop or am idling in traffic. It's very intermittent, but when it happens, the engine just cuts out, and I have to restart it.

Besides the stalling, the engine also feels a bit rough at idle, not as smooth as it used to be. There hasn't been a check engine light yet, which makes it harder to diagnose. Has anyone with a 2016-2019 LaCrosse experienced similar stalling or rough idle without a CEL? What was the cause?

I'm looking for any ideas on what might be causing this before I take it to a mechanic. It's becoming a safety concern. Thanks for any help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:44 AM

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ClearTheCode admin answer:

Stalling at idle and rough running in your 2018 Buick LaCrosse, even without a check engine light, can be caused by several factors related to the engine's ability to maintain a stable idle and proper air-fuel mixture.

Common Causes:

  1. Dirty or Faulty Throttle Body: Carbon buildup on the throttle plate can restrict airflow at idle, causing the engine to stall or run rough. A faulty electronic throttle body can also cause erratic idle control.
  2. Vacuum Leaks: Leaks in vacuum hoses, the intake manifold gasket, or PCV system can introduce unmetered air, leaning out the air-fuel mixture and causing rough idle or stalling.
  3. Mass Air Flow (MAF) Sensor: A dirty or failing MAF sensor can send incorrect air mass readings to the Engine Control Module (ECM), leading to an improper air-fuel ratio, especially at idle.
  4. Fuel Delivery Issues:
    • Clogged Fuel Filter: Restricts fuel flow, leading to fuel starvation at low RPMs.
    • Weak Fuel Pump: May not provide consistent fuel pressure, especially under varying loads.
    • Failing Fuel Pressure Regulator: Can cause incorrect fuel pressure, affecting engine performance.
  5. Ignition System: While less likely without a CEL, weak spark plugs or ignition coils could contribute to rough idle.

Diagnostics & What to Do:

  1. Inspect the Throttle Body: A visual inspection can reveal carbon buildup. Cleaning the throttle body is a relatively easy DIY task, but ensure you use throttle body cleaner, not carburetor cleaner.
  2. Check for Vacuum Leaks: Listen for a hissing sound around hoses and the intake manifold. A smoke test by a mechanic is the most effective way to find small leaks.
  3. Monitor Fuel Pressure: A mechanic can connect a fuel pressure gauge to monitor pressure at idle and under load to rule out fuel delivery problems.
  4. Scan for Pending Codes: Even without a solid check engine light, there might be 'pending' codes stored in the ECM that haven't triggered the light yet. A good OBD-II scanner can read these.

When to See a Shop:

Given that stalling can be a safety hazard, you should have your LaCrosse inspected by a professional mechanic as soon as possible. They have specialized diagnostic tools to accurately pinpoint the issue, such as live data monitoring for MAF readings, fuel trims, and fuel pressure. Do not wait for the problem to worsen or for a check engine light to appear, as this could indicate a more severe underlying issue.

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