Cylinder 8 Contribution/Balance Fault
The P0284 code indicates that the engine control module (ECM) has detected a misfire or imbalance in cylinder 8, meaning that cylinder is not contributing equally to engine power compared to the other cylinders. This can be caused by issues with fuel delivery, ignition, or mechanical problems within that cylinder.
1. Most Common Causes
- Faulty fuel injector on cylinder 8 (electrical or clogged)
- Low compression in cylinder 8 (worn rings, leaking valves, blown head gasket)
- Wiring or connector issues for injector 8 (open or short circuit)
- Internal engine mechanical failure (camshaft, lifters, valve springs)
- Faulty PCM or programming error (rare)
2. Symptoms You Will Notice
- Check Engine Light on
- Engine misfire or rough idle
- Reduced engine power and acceleration
- Poor fuel economy
- Engine vibration at idle
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Perform a cylinder contribution test using a scan tool to confirm cylinder 8 imbalance.
Step 3: Inspect spark plug and ignition coil on cylinder 8; swap with another cylinder to see if misfire follows.
Step 4: Check fuel injector on cylinder 8; perform a balance test or swap injectors.
Step 5: Perform a compression test on cylinder 8 and compare to other cylinders.
Step 6: Inspect for vacuum leaks around intake manifold and cylinder 8 area.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code as it can cause catalytic converter damage and reduced engine performance. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost varies depending on the root cause. A simple spark plug replacement may cost $50-$150, while a fuel injector replacement can range from $200-$600. Diagnostic fees are typically $100-$150.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.