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2020 Pacifica Rough Idle & CEL - P0304 Misfire

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Emily N. · rep 0 · May 22, 4:58 AM · 1 replies · solved · Question

Vehicle: 2020 Chrysler Pacifica Touring L

Hey everyone,

My 2020 Chrysler Pacifica Touring L just threw a Check Engine Light, and it's been running a bit rough, especially at idle. It feels like a slight shudder, and the fuel economy seems to have dipped a little.

I used my OBD-II scanner and pulled a P0304 code, which points to a misfire on cylinder 4. I'm trying to figure out the most common causes for this on a Pacifica of this vintage before I start tearing things apart.

Has anyone else experienced a P0304 on their 2016-2026 Pacifica? What was the fix? I'm hoping it's something relatively straightforward like a spark plug or coil pack, but I'm open to any suggestions for troubleshooting steps.

Thanks in advance for any help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:58 AM

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ClearTheCode admin answer:

A P0304 code indicates a misfire detected in cylinder 4. This is a common diagnostic trouble code, and while it points to a specific cylinder, the underlying cause can vary. Here's a breakdown of common causes and troubleshooting steps for your 2020 Chrysler Pacifica Touring L:

Common Causes for P0304:

  1. Faulty Spark Plug: A worn, fouled, or damaged spark plug in cylinder 4 is a very common culprit.
  2. Ignition Coil Failure: The ignition coil responsible for cylinder 4 might be failing or completely dead.
  3. Fuel Injector Issues: A clogged, dirty, or malfunctioning fuel injector for cylinder 4 can prevent proper fuel delivery.
  4. Vacuum Leaks: Less common for a single cylinder misfire, but a significant vacuum leak near cylinder 4 could contribute.
  5. Low Compression: Internal engine issues like a bad valve, head gasket, or piston ring could lead to low compression in cylinder 4, causing a misfire.

Troubleshooting Steps:

  1. Inspect Spark Plug: Remove the spark plug from cylinder 4. Look for signs of wear, oil fouling, or damage. If it looks bad, replace it. Consider replacing all spark plugs if they are due for maintenance.
  2. Swap Ignition Coil: To confirm if the coil is the issue, swap the ignition coil from cylinder 4 with a coil from a different cylinder (e.g., cylinder 2). Clear the code and drive the vehicle. If the misfire moves to the new cylinder (e.g., P0302 appears), the coil is faulty.
  3. Check Fuel Injector: This is harder to diagnose without specialized tools. You can listen to the injector with a stethoscope for a consistent clicking sound. If you suspect the injector, a professional can test its pulse and spray pattern. You could also try swapping it with another cylinder's injector, similar to the coil test, but this is more involved.
  4. Compression Test: If the above steps don't resolve the issue, perform a compression test on cylinder 4 and compare it to the other cylinders. Significant differences indicate an internal engine problem.

When to See a Shop:

  • If you've performed the basic spark plug and coil swap tests and the issue persists or points to a fuel injector.
  • If you suspect low compression, as this indicates a more serious internal engine problem requiring professional diagnosis and repair.
  • If the Check Engine Light is flashing, which indicates a severe misfire that could damage the catalytic converter. Stop driving immediately and have it towed to a reputable mechanic.
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