P0307 serious

Cylinder 7 Misfire Detected

What does P0307 mean?

The P0307 code means the vehicle's onboard diagnostic system has detected: Cylinder 7 Misfire Detected. This is a serious severity code.

Common Symptoms

  • Rough idle on V8 engine
  • Check Engine Light on
  • Power loss

Probable Causes (Ranked by Likelihood)

  • Faulty spark plug on cylinder 7 Very High
  • Failed ignition coil on cylinder 7 High
  • Clogged fuel injector on cylinder 7 High
  • Low compression on cylinder 7 Moderate

Step-by-Step Diagnostic Procedure

  1. Swap cylinder 7 coil and spark plug. Confirm whether the misfire follows the component.

  2. Injector balance test on cylinder 7.

  3. Compression test as a final diagnostic step.

Frequently Asked Questions

Where is cylinder 7 on a V8?

On most GM V8 engines (LS family), cylinder 7 is the fourth cylinder on the passenger side (right bank). On Ford V8 engines, cylinder 7 is the third cylinder on the passenger side. Consult your service manual for exact location.

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