Step-by-Step VQ37VHR P0300 & P117B Diagnostic & Fix
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1. Initial Fault Scanning
Use an OBD-II scanner to pull the codes. A P0300 indicates a random multiple misfire, but look for specific cylinder codes like P0304 (Cylinder 4) to narrow your search.
2. Visual Inspection of the Intake System
Before buying parts, check the basics. Inspect the dual air filters for heavy clogs and examine the intake boots and PCV hoses for cracks or tears. A vacuum leak here will often trigger the P117B air-fuel ratio code.
3. The Coil Pack Swap Test
To confirm a failing part, swap the coil pack from the misfiring cylinder (e.g., Cylinder 4) to a known good cylinder (e.g., Cylinder 2).
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Note: On the VQ37VHR, even cylinders (2, 4, 6) are on the driver’s side.
4. Confirming the Failure
Clear the codes and restart the engine. If the misfire follows the coil to the new location (e.g., code changes to P0302), you have confirmed the coil pack is defective.
5. Installation and Final Road Test
Install a fresh coil pack, clear all remaining codes, and let the car idle to ensure the engine is no longer shaking. Finish with a test drive to ensure the air-fuel ratio stays within spec under load.
Watch the full video here: https://youtu.be/9SP--eXCDUM
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