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2022 Yukon AT4 - Engine Hesitation, Poor MPG, Occasional Rough Idle

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Mike T. · rep 0 · May 22, 3:39 AM · 1 replies · solved · Question

Vehicle: 2022 GMC Yukon AT4

Hello forum,

I'm experiencing some concerning issues with my 2022 GMC Yukon AT4, which has the 6.2L V8 engine and about 35,000 miles. Lately, I've noticed a distinct hesitation during acceleration, especially from a stop or when trying to pass. My fuel economy has also taken a hit, dropping a couple of MPG.

Occasionally, it will have a slightly rough idle, almost like a very subtle misfire, but the check engine light hasn't come on. I'm wondering if this could be related to the Active Fuel Management (AFM) or Dynamic Fuel Management (DFM) system, or perhaps a fuel delivery issue. It's still under warranty, but I want to go in with some knowledge.

Has anyone with a newer Yukon or Sierra experienced similar symptoms? Any thoughts on what might be causing this?

✓ Accepted solution

ClearTheCode Admin

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

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ClearTheCode admin answer:

Your 2022 GMC Yukon AT4's symptoms of hesitation, poor fuel economy, and occasional rough idle, especially with the 6.2L V8, could indeed be related to several factors, including the advanced fuel management systems (AFM/DFM). Here's a breakdown:

Potential Causes:

  1. Active/Dynamic Fuel Management (AFM/DFM) Issues: These systems deactivate cylinders to save fuel. Problems can arise from:
    • Lifter Failure: Collapsed or sticking lifters are a known issue with these systems, leading to misfires and rough running, especially when switching between V4 and V8 modes.
    • AFM/DFM Solenoids: Faulty solenoids can prevent proper cylinder deactivation/reactivation.
  2. Fuel System Problems:
    • Clogged Fuel Injectors: Even at 35,000 miles, a partially clogged injector can cause hesitation and reduced fuel efficiency.
    • Fuel Pump/Pressure Issues: A weakening fuel pump or issues with the high-pressure direct injection system can lead to insufficient fuel delivery.
  3. Ignition System: While less likely without a CEL, a weak spark plug or coil could contribute to subtle misfires.
  4. Mass Air Flow (MAF) Sensor: A dirty or failing MAF sensor can send incorrect air-fuel mixture data to the ECU, leading to performance issues.

Diagnostics & When to See a Shop:

  • Retrieve OBD-II Codes: Even without a CEL, a professional scanner can often pull pending or history codes. Look for P0300 (Random/Multiple Cylinder Misfire), P0171/P0174 (System Too Lean Bank 1/2), or specific AFM/DFM related codes.
  • Fuel System Check: A technician can test fuel pressure and inspect fuel injector performance.
  • AFM/DFM System Diagnosis: This requires specialized diagnostic tools to monitor cylinder deactivation/reactivation and lifter operation. A shop can perform a 'cylinder drop test' to identify misfiring cylinders.
  • Under Warranty: Since your Yukon is still under warranty, it's crucial to take it to a GMC dealership. Document all your symptoms clearly. They have access to service bulletins and specific diagnostic procedures for these known issues. Be persistent if the initial diagnosis doesn't resolve the problem, as AFM/DFM issues can sometimes be tricky to pinpoint.
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