P0304 on Pontiac
Cylinder 4 Misfire Detected
P0304 on Pontiac vehicles indicates cylinder 4 misfire detected. Au7o has documented this code across 1 Pontiac model — most commonly on Sunfire. 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 Pontiac range from $1,000 to $2,500, 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 Pontiac by Model
Pontiac Sunfire(1 issue)
- Sunfire 2.2L Ecotec (L61) Head Gasket / Head Crack2002-2005
The first-generation 2.2L Ecotec L61 in 2002-2005 Sunfire (and Cobalt, Cavalier, Saturn Ion) is prone to head gasket failure and cylinder head cracking — particularly if overheated once. Aluminum head warps easily. Often presents as bubbles in coolant reservoir, white smoke, and overheating.
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What does P0304 mean on Pontiac?▼
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 Pontiac specifically, this code is documented across 1 model.
What causes P0304 on Pontiac vehicles?▼
Common causes on Pontiac: 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 Pontiac?▼
Repair costs on Pontiac range from $1,000 to $2,500, depending on the specific model and root cause.
Which Pontiac models have P0304 documented?▼
Au7o has documented P0304 on 1 Pontiac model: Sunfire.