Random misfire

Good morning,

The most common cause for the 300 misfire code is low fuel pressure from a weak fuel pump.

You need to test the fuel pressure to verify.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Fuel Pressure (Key ON, Engine OFF) .................... 284-325 kPa (41-47 psi)

It looks like you may be replacing the fuel pump.

Roy

FUEL SENDER ASSEMBLY REPLACEMENT

REMOVAL PROCEDURE

CAUTION: Fuel Vapors can collect while servicing fuel system parts in enclosed areas such as a trunk. To reduce the risk of fire and increased exposure to vapors:
- Use forced air ventilation such as a fan set outside of the trunk.
- Plug or cap any fuel system openings in order to reduce fuel vapor formation.
- Clean up any spilled fuel immediately.
- Avoid sparks and any source of ignition.
- Use signs to alert others in the work area that fuel system work is in process.

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1. Relieve the fuel system pressure.
2. Drain the fuel tank. Refer to Fuel Tank Draining Procedure.
3. Remove the rear compartment trim panel.
4. Remove the fuel sender access panel bolts.
5. Remove the fuel sender access panel.

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6. Disconnect the fuel sender quick-connect fittings.

NOTE: In order to prevent damage, cover the fuel pipe fittings with a shop towel before disconnecting the fuel pipes or removal of the fuel sender retaining ring, in order to catch any fuel that may leak out. Place the towel in an approved container when procedure is completed.

7. Disconnect the fuel sender electrical connector.
8. Disconnect the fuel tank pressure sensor electrical connector.
9. Remove the fuel sender retaining ring using the fuel sender lock nut wrench.

IMPORTANT: The modular fuel sender assembly will spring-up when the locking ring is removed.

10. Remove the fuel sender assembly.

NOTE: Do Not handle the fuel sender assembly by the fuel pipes. The amount of leverage generated by handling the fuel pipes could damage the joints.

IMPORTANT: When removing the fuel sender assembly from the fuel tank, the reservoir bucket on the fuel sender is full of fuel. The fuel sender must be tipped slightly during removal in order to avoid damage to the float. Place any remaining fuel into an approved container once the fuel sender is removed from the fuel tank.

11. Clean the fuel sender sealing surfaces.
12. Inspect the fuel sender sealing surfaces.