Fix a cylinder misfire by determining where it is occurring, diagnosing the problem and replacing defective parts. Use an engine scan tool to help isolate the problem cylinder and likely cause of the misfire. The time to complete the process depends on the cause of the misfire.
- Determine the problem location
Attach the scan tool to the OBDII port to retrieve the diagnostic code. A P0200 series code generally indicates a problem with a fuel injector, while a P0300 series code indicates another issue, often with the spark plug or wire. If the code replaces the final zero in either of these codes with another number, it indicates the cylinder where the problem is occurring. If the code has a zero as the final digit, the problem is affecting two or more cylinders. Using the scan tool prevents damage to the electronics caused by the older method of removing plug wires one at a time to find the issue.
- Diagnose the problem
If the tool returned a P0300 series code, remove the indicated plug wire and inspect it for damage. Bend the wire and look for cracks. Check the wire boot for damage. Remove the plug, and inspect it. There should be no cracks in the porcelain, and the electrode should be dry and brown in color with a hint of green.
- Replace defective parts
Replace any plugs or wires found to be defective. Test-drive the vehicle to verify that the misfire is eliminated.