The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2020 Acadia Denali Rough Idle & Misfire - Check Engine Light On

0

Jason D. · rep 0 · May 22, 3:39 AM · 1 replies · solved · Question

Vehicle: 2020 GMC Acadia Denali

Hi all,

My 2020 GMC Acadia Denali (3.6L V6) recently started acting up. I've got about 60,000 miles on it. It developed a really rough idle, especially when cold, and feels like it's shaking more than usual. The check engine light came on yesterday, and I've noticed a slight decrease in power and fuel economy.

I haven't had a chance to get the codes read yet, but it definitely feels like a misfire. Could it be spark plugs, ignition coils, or something more serious? Any common issues with the 3.6L in these model years that might cause this?

Any advice on what to look for or common culprits would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

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

0

ClearTheCode admin answer:

It sounds like your 2020 GMC Acadia Denali is indeed experiencing an engine misfire, which is a common cause for a rough idle and the Check Engine Light (CEL). Here's what's likely happening and what steps to take:

Common Causes of Misfires in the 3.6L V6:

  1. Ignition System Issues: This is the most frequent cause.
    • Spark Plugs: Worn or fouled spark plugs can lead to incomplete combustion. At 60,000 miles, they might be due for inspection or replacement, though many are rated for longer.
    • Ignition Coils: A failing ignition coil for a specific cylinder will prevent the spark plug from firing correctly.
  2. Fuel System Problems:
    • Fuel Injectors: A clogged or faulty fuel injector can starve a cylinder of fuel.
    • Low Fuel Pressure: Issues with the fuel pump or fuel pressure regulator can affect all cylinders.
  3. Air/Vacuum Leaks: Unmetered air entering the engine can lean out the air-fuel mixture, causing misfires.
  4. Compression Issues: Less common, but internal engine problems like worn piston rings or valve issues can reduce cylinder compression.

Diagnostics & When to See a Shop:

  • Retrieve OBD-II Codes: This is your first step. A misfire will almost certainly trigger a P030X code (e.g., P0301 for Cylinder 1 Misfire, P0302 for Cylinder 2, etc.). You might also see codes like P0420/P0430 (Catalyst System Efficiency Below Threshold) if the misfire has been ongoing and damaged the catalytic converter.
  • Identify Misfiring Cylinder: The P030X code will tell you which cylinder is misfiring. Once identified, you can swap the spark plug and/or ignition coil with an adjacent cylinder to see if the misfire moves. If it does, you've found the faulty component.
  • Inspect Spark Plugs: Visually inspect the spark plugs for wear, fouling, or damage.
  • Fuel System Check: If ignition components are ruled out, a shop can test fuel pressure and injector pulse.
  • Professional Help: If you're not comfortable with DIY diagnostics, or if the problem persists after checking basic ignition components, it's best to take your Acadia to a qualified mechanic. They can perform more advanced tests like compression checks or smoke tests for vacuum leaks.
Menu

Help & account