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2017 Canyon Misfire and Rough Idle - Spark Plugs or Coils?

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Kevin B. · rep 0 · May 22, 3:45 AM · 1 replies · solved · Question

Vehicle: 2017 GMC Canyon SLT

Hello everyone,

I'm having some trouble with my 2017 GMC Canyon SLT, 3.6L V6, which has about 90,000 miles on it. Recently, I've noticed a rough idle, especially when stopped at a light, and a slight hesitation or misfire under light acceleration. The 'Check Engine' light also came on and is now staying on.

I used an OBD-II scanner and pulled a P0304 code, which indicates a misfire on cylinder 4. I haven't changed the spark plugs yet, and I'm wondering if that's the most likely culprit, or if I should be looking at the ignition coils too.

Any advice on diagnosing this further or if this is a common issue at this mileage?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:45 AM

0

ClearTheCode admin answer:

A P0304 diagnostic trouble code (DTC) specifically points to a misfire in cylinder 4 of your 2017 GMC Canyon's 3.6L V6 engine. At 90,000 miles, both spark plugs and ignition coils are common wear items that can cause this issue.

Here's a systematic approach to diagnose and resolve the misfire:

  1. Spark Plugs: Given your mileage, worn spark plugs are a very strong candidate. Over time, the electrode gap widens, and carbon deposits can build up, leading to a weaker spark and misfires. The 3.6L V6 typically uses iridium-tipped plugs with a service interval often around 100,000 miles, but conditions can accelerate wear.
  2. Ignition Coils: Each cylinder has its own ignition coil (coil-on-plug system). A failing coil can intermittently or completely fail to provide sufficient voltage to the spark plug, causing a misfire. They can fail due to age, heat, or internal defects.
  3. Fuel Injector: A clogged or faulty fuel injector for cylinder 4 could also cause a lean condition and misfire. This is less common than plugs or coils but still a possibility.
  4. Compression Issue: In rare cases, a misfire can be due to low compression in the cylinder, indicating an internal engine problem (e.g., worn piston rings, valve issues).

DIY Diagnostic Steps (if comfortable):

  • Swap Components: To confirm if it's the coil or plug, you can swap the ignition coil from cylinder 4 to an adjacent cylinder (e.g., cylinder 2) and clear the code. If the misfire code changes to P0302, then the coil is bad. Do the same for the spark plug if the coil swap doesn't isolate the issue.
  • Visual Inspection: When you remove the spark plug from cylinder 4, inspect its condition. Look for excessive wear, oil fouling, or unusual deposits.

When to See a Shop:

  • If Unsure: If you're not comfortable performing the diagnostic swaps or replacing the components yourself.
  • Persistent Misfire: If replacing the spark plug and/or coil for cylinder 4 doesn't resolve the issue, a shop can perform more advanced diagnostics, such as fuel pressure tests, injector pulse tests, and compression tests, to pinpoint the exact cause.
  • Multiple Misfires: If you start getting multiple misfire codes (P030x for several cylinders), it might indicate a broader issue or a need for a full set of spark plugs and coils.
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