Cylinder 3 Misfire Detected
Fix P0303 cylinder 3 misfire code. Learn how to diagnose a single-cylinder misfire from ignition to fuel to compression.
Engine Problems
Symptoms
- 1Check engine light on (may flash)
- 2Rough idle and vibration
- 3Hesitation or stumbling
- 4Loss of power
- 5Poor fuel economy
Common Causes
- 1Faulty spark plug or ignition coil on cylinder 3
- 2Clogged or failed fuel injector
- 3Vacuum leak affecting that cylinder
- 4Low compression (valve or ring issue)
- 5Damaged wiring to the coil or injector
How to Fix
- 1Inspect and replace the spark plug for cylinder 3
- 2Swap the coil to another cylinder to test
- 3Test the fuel injector operation
- 4Check compression on cylinder 3
- 5Inspect wiring and connectors to the cylinder
What Does P0303 Mean?
The P0303 code indicates that the ECM detected a misfire in cylinder 3 specifically. A misfire means that cylinder isn't burning the air/fuel mixture properly.A Targeted Diagnosis
Because P0303 points to one cylinder, you can swap components like the coil or injector to that cylinder and see if the misfire follows - a quick way to isolate the cause.The Three Pillars
Misfires come down to spark, fuel, or compression. Check ignition components first, then the injector, then mechanical compression.How AI4Car Helps
AI4Car can show misfire counts per cylinder and fuel trim data, helping you confirm cylinder 3 and watch whether the misfire moves after a repair.Related Codes
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