P0284Powertrain
Powertrain · SAE
Cylinder 8 Contribution/Balance — Deviation
Meaning
The ECM has detected that cylinder 8 is delivering a significantly different fuel quantity compared to the other cylinders. The cylinder balance/contribution monitor has detected an imbalance exceeding the allowable tolerance threshold.
Common causes
- Worn, clogged, or flow-drifted injector on cylinder 8
- Low compression on cylinder 8 (valves, rings, head gasket)
- Fuel circuit restriction or leak at cylinder 8
- Faulty spark plug or ignition coil (8-cylinder gasoline engines)
- Common rail pressure sensor drift (diesel engines)
- Intake manifold leak at cylinder 8 port
Symptoms
- Malfunction indicator lamp (MIL) illuminated
- Sporadic misfire or torque imbalance at cylinder 8
- Vibrations at idle or under load
- Abnormal fuel consumption
- Possible exhaust smoke
Severity
Moderate: prolonged imbalance can lead to misfire, catalytic converter damage, and degraded performance on V8 or inline-8 engines.
What to do
- Perform injector balance/contribution test with a scan tool (cut-out test)
- Check cylinder 8 compression pressure
- Inspect and test cylinder 8 injector (flow rate, seal, spray pattern)
- Check spark plug and coil (gasoline) or common rail system (diesel)
- Replace injector if flow is out of specification