Cylinder 4 Misfire Detected - Causes & Fixes
Learn what P0304 means, why cylinder 4 is misfiring, and how to fix it. Complete guide with symptoms, causes, and step-by-step solutions.
What you may notice
Symptoms
- 01Check engine light flashing or steady
- 02Rough idle or engine vibration
- 03Lack of power during acceleration
- 04Poor fuel economy
- 05Engine hesitation or stumbling
Where to look first
Common causes
- 01Worn or fouled spark plug in cylinder 4
- 02Faulty ignition coil on cylinder 4
- 03Damaged spark plug wire or boot
- 04Vacuum leak near cylinder 4
- 05Low fuel pressure or clogged fuel injector
- 06Low compression in cylinder 4
A sensible sequence
Best diagnostic order
- 01Review freeze-frame data and locate cylinder 4.
- 02Inspect and swap the plug and coil one at a time.
- 03Test the injector circuit, intake sealing, and compression.
Step by step
What to check and repair
- 01Replace the spark plug in cylinder 4
- 02Test and replace the ignition coil if faulty
- 03Inspect and replace spark plug wires if damaged
- 04Check for vacuum leaks and repair
- 05Test fuel injector and clean or replace
- 06Perform a compression test if other fixes fail
What Does P0304 Mean?
The P0304 code indicates that your vehicle's engine control module (ECM) has detected a misfire in cylinder 4. A misfire occurs when the air-fuel mixture in a cylinder fails to ignite properly, leading to reduced engine performance and potential damage if left unaddressed.
Why Is This Code Important?
Cylinder misfires can cause serious problems including: - Increased emissions and failed emissions tests - Damage to the catalytic converter (expensive repair) - Poor fuel economy - Engine damage if ignored long-term
How AI4Car Helps
Our AI-powered diagnostic tool can help you understand the severity of the P0304 code in your specific vehicle, provide personalized recommendations, and track whether the issue returns after repairs.