P0300 Multiple Cylinder Misfire

NAME OF CODE
Multiple Cylinder Misfire

WHEN MONITORED
With the engine running, after successfully performing a crank sensor learn.

SET CONDITION
When more than a 2% misfire rate is measured during two trips, or with a 10% to 0% misfire rate during one trip.

THEORY OF OPERATION
Misfire is detected by the crankshaft speed fluctuation (CSF) method. This method compares the engine speed difference between the cylinders in firing order. The speed is detected by the crankshaft position sensor. When a large enough RPM difference occurs between cylinders, a misfire count of 1 recorded. Two types of misfire are detected: a two-trip misfire, which is about 2% and results in an emissions increase, or a one-trip misfire, which is about 0-30% and will cause damage to the catalytic converter.

POSSIBLE CAUSES
- Secondary ignition wires
- Fuel pump or filter
- Injector harness connectors
- Ignition coil circuit
- Spark plug
- Mechanical engine problem
- Contaminated fuel
- Water in fuel
- PCM power grounds
- Injectors
- Restricted exhaust
- Intake restriction
- PCM
- EVAP system
- EGR system
- Air gap at high RPM'S
- Mechanical
- Damaged trigger wheel