P0304 on Peugeot
Cylinder 4 Misfire Detected
P0304 on Peugeot vehicles indicates cylinder 4 misfire detected. Au7o has documented this code across 2 Peugeot models — most commonly on 206, 308. This code means the engine computer detected a misfire in cylinder number 4 — that cylinder isn't igniting its air-fuel mixture fully or at all. The system detects this by monitoring small changes in crankshaft rotation speed as each cylinder fires. You may feel a rough idle, shaking, hesitation or reduced power, and a persistent misfire can dump unburned fuel into the exhaust and overheat or damage the catalytic converter. Since it's pinpointed to one cylinder, the problem typically lies in that cylinder's spark, fuel, or compression. Typical repair costs on Peugeot range from $80 to $900, depending on the specific model and root cause.
Common Causes of P0304
- •Worn or fouled spark plug in cylinder 4
- •Failed or weak ignition coil on cylinder 4
- •Faulty spark plug wire or boot (where applicable)
- •Clogged, stuck or leaking fuel injector for cylinder 4
- •Vacuum or intake air leak near that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Damaged wiring or connector at the coil or injector
P0304 on Peugeot by Model
Peugeot 206(1 issue)
- Ignition Coil Pack Failure (Petrol TU Engines)1998-2012
The wasted-spark coil pack on the 206's small petrol engines (1.1 KFV, 1.4 KFW and related TU units) is a frequent failure item: one of the two internal coils breaks down, dropping spark on a paired set of cylinders (1/4 or 2/3). Owners report intermittent misfire, rough running, the engine cutting out and refusing to restart until it cools, and the management light flickering. Forum consensus also warns that cheap aftermarket replacement packs often fail repeatedly or seat poorly, causing the fault to return.
Peugeot 308(1 issue)
- 1.6 THP Intake Valve Carbon Buildup (Direct Injection)2008-2017
Because the turbocharged 1.6 THP (EP6DT/EP6CDT/EP6DTS) injects fuel directly into the cylinder, no fuel washes over the backs of the intake valves; oil vapour from the PCV system bakes onto the valves and ports as hard carbon. Deposits typically become symptomatic between 50,000 and 80,000 km, progressively restricting airflow and causing rough cold idle, cold-start misfires, poor throttle response and higher fuel consumption.
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View P0304 across all makes →Frequently Asked Questions
What does P0304 mean on Peugeot?▼
P0304 stands for "Cylinder 4 Misfire Detected." This code means the engine computer detected a misfire in cylinder number 4 — that cylinder isn't igniting its air-fuel mixture fully or at all. The system detects this by monitoring small changes in crankshaft rotation speed as each cylinder fires. You may feel a rough idle, shaking, hesitation or reduced power, and a persistent misfire can dump unburned fuel into the exhaust and overheat or damage the catalytic converter. Since it's pinpointed to one cylinder, the problem typically lies in that cylinder's spark, fuel, or compression. On Peugeot specifically, this code is documented across 2 models.
What causes P0304 on Peugeot vehicles?▼
Common causes on Peugeot: Worn or fouled spark plug in cylinder 4, Failed or weak ignition coil on cylinder 4, Faulty spark plug wire or boot (where applicable), Clogged, stuck or leaking fuel injector for cylinder 4, Vacuum or intake air leak near that cylinder. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0304 on a Peugeot?▼
Repair costs on Peugeot range from $80 to $900, depending on the specific model and root cause.
Which Peugeot models have P0304 documented?▼
Au7o has documented P0304 on 2 Peugeot models: 206, 308.