Faulty ignition coil or spark plug on cylinder 8; Faulty or blocked fuel injector on cylinder 8 (stuck open, stuck closed or poor spray pattern); Wiring or connector fault to the cylinder 8 injector or coil, such as chafing, corrosion or a loose pin; Vacuum or intake leak near cylinder 8, such as a split manifold gasket or hose; Low compression on cylinder 8 from a burnt valve, worn rings or head gasket leak; Valvetrain fault on cylinder 8, such as a collapsed lifter, worn cam lobe or sticking valve (depends on engine design); Fault in the engine control unit driver circuit for cylinder 8.

P0284

Cylinder 8 Contribution/Balance.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
84: FaultThe specific fault in that area

What it means

P0284 means the engine control unit has found that cylinder 8 is contributing far less (or sometimes far more) to engine output than the other cylinders. It sets when the cylinder balance or contribution test, based on crankshaft speed changes, shows cylinder 8 outside its allowed limits. The code does not say why, so the fault could lie in ignition, fuel, air or mechanical condition.

Symptoms

Rough idle and a noticeable engine shake
Misfire or hesitation under load
Loss of power and poor acceleration
Increased fuel consumption
Engine management light on, possibly flashing under load
Fuel smell or raw fuel in the exhaust

Possible causes

Faulty ignition coil or spark plug on cylinder 8likely
Faulty or blocked fuel injector on cylinder 8 (stuck open, stuck closed or poor spray pattern)likely
Wiring or connector fault to the cylinder 8 injector or coil, such as chafing, corrosion or a loose pinpossible
Vacuum or intake leak near cylinder 8, such as a split manifold gasket or hosepossible
Low compression on cylinder 8 from a burnt valve, worn rings or head gasket leakpossible
Valvetrain fault on cylinder 8, such as a collapsed lifter, worn cam lobe or sticking valve (depends on engine design)rare
Fault in the engine control unit driver circuit for cylinder 8rare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine load, speed and temperature when the fault set. Look for related misfire codes, especially P0308.
Check live data for misfire counts or cylinder balance values to confirm cylinder 8 is the weak one.
Visually inspect the cylinder 8 coil, injector connectors and wiring for damage, oil contamination, corrosion or looseness.
Remove the cylinder 8 spark plug and examine it for wear, fouling, damage or signs of oil or fuel.
Swap the cylinder 8 coil with another cylinder, then see whether the fault follows the coil. Repeat for the injector if the engine design allows.
Test injector resistance and check for the correct injector pulse signal and power supply at the connector.
Inspect for intake leaks around the manifold and vacuum hoses, and check fuel pressure against the manufacturer specification.
If the fault remains, carry out compression and leak-down tests on cylinder 8, and inspect the valvetrain as the engine design requires.

How to fix

Replace the faulty ignition coil and/or spark plug on cylinder 8, and consider renewing the plugs as a set if they are worn.
Clean or replace the cylinder 8 fuel injector if testing shows it is blocked or leaking.
Repair or replace damaged wiring, terminals or connectors in the cylinder 8 circuit.
Repair the intake leak by replacing the failed gasket, seal or hose.
Carry out the necessary engine repair for low compression or valvetrain faults, such as valve, piston ring, head gasket or lifter work.

Can I keep driving?

Medium severity

Short, gentle driving to a workshop is usually acceptable, but avoid heavy loads. If the warning light flashes or the engine runs very roughly, stop driving, as unburnt fuel can damage the catalytic converter.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.