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2004 Chevrolet Impala 3.4L OBD2 Code P0304 - Misfire Diagnosis & Fixes

Model: 2004 3.4 Impala Fault Code: P0304 Posted: 2017-02-07 08:11

I own a 2004 Chevrolet Impala with a 3.4L engine and recently received OBD2 diagnostic code P0304. This indicates a misfire in cylinder #4. I'm seeking advice on possible causes and troubleshooting steps to resolve this issue. The P0304 code typically points to one of the following root causes: - IGNITION system failure: no spark or weak spark in cylinder 4 - INJECTION issues: faulty injector, leaking, clogged, or failing to pulse properly - MECHANICAL problems: low compression or vacuum leaks For reference, detailed explanations and troubleshooting can be found at https://www.obd-codes.com/p0304

Related fault codes
P0304
Comments (3)
Anonymous 2017-02-07 09:06

P0304 indicates a misfire in cylinder #4. Common causes include: - Ignition system failure (no spark or weak spark) - Injector problems (bad, leaking, clogged, or not pulsing) - Mechanical issues such as low compression or vacuum leaks More details available at: https://www.obd-codes.com/p0304

Anonymous 2017-02-08 06:18

Thanks for the clear explanation! This helps me understand what I'm dealing with and where to start troubleshooting.

Anonymous 2017-05-03 13:08

On my 2006 HHR 2.4L, I've experienced recurring check engine lights that trigger traction control and cause hard shifting. The codes are consistently P0304 and occasionally P0107. I initially suspected fuel rail contamination and performed a compression test, which showed no major issues. At one point, I noticed the crankcase ventilation hose [12599243] was old and cracked. After replacing it with a generic hose, symptoms improved—but returned worse after a follow-up compression test. During that test, I identified the real issue: the outlet duct [25937095] is torn at its connection point to the CV hose. I temporarily taped it shut, and since then, the P0304 code has not reappeared. This suggests a vacuum leak in that area may be directly causing the misfire.