Cylinder Misfire

Name of Code:
Cylinder #1. #2. #3. #4. #5. #6 Misfire

When Monitored:
With the engine running, after successfully performing a crank sensor learn, and with engine RPM below 3,000.

Set Condition:
When more than a 2% misfire rate is measured during two trips, or with a 10% to 12% 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. An RPM value is set for each cylinder for comparison. When an RPM difference of approximately 1 to 10 occurs between cylinders. a misfire count of 1 is recorded. The RPM can vary between 1 and 10 because of different input variables. 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 10-20% and will cause damage to the catalytic converter.

Possible Causes:
- Ignition coil circuit
- Spark plug, wire, or connector
- Fuel pump or filter
- Mechanical engine problem
- EGR system
- Injectors
- Faulty connections
- PCM