Applicable Systems
OBD-II
Symptoms
Cylinder 3 misfiring; rough idle, power loss; CEL on or flashing.
Possible Causes
- Worn spark plug
- Faulty ignition coil
- Clogged injector
- Burned valve or low compression
Troubleshooting Steps
- Step 1: Swap test: spark plug to adjacent cylinder
If misfire moves, plug is bad - Step 2: Swap test: ignition coil
If misfire moves, coil is bad - Step 3: Compression test cylinder 3
Compression within spec - Step 4: Injector noid test
Injector pulses - Step 5: Replace faulty component
No misfire on cyl 3
How to Reset
Clear with OBD-II scanner.
Common Replacement Parts
- Spark Plug (OEM spec)
- Ignition Coil (OEM spec)
Frequently Asked Questions
- Q: Can vacuum leak cause single-cylinder misfire?
Rarely. Vacuum leak usually affects multiple cylinders. Single-cylinder misfire more likely spark plug, coil, or injector.
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Source: SAE J2012 standard DTC list + OBD-II portal
Category: OBD-II
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