Worn, fouled or incorrectly gapped spark plug on cylinder 7; Faulty ignition coil or coil connector on cylinder 7; Faulty or blocked fuel injector on cylinder 7, or a wiring fault to it; Vacuum or intake leak affecting cylinder 7, such as a damaged intake manifold gasket; Low compression on cylinder 7 due to a burnt valve, worn piston rings or a head gasket leak; Wiring or connector damage in the ignition or injector circuit for cylinder 7; Valve train problem such as a worn camshaft lobe, collapsed lifter or valve timing fault.

P0307

Cylinder 7 Misfire Detected.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
07: FaultThe specific fault in that area

What it means

P0307 means the engine control unit has detected misfiring on cylinder 7, which only applies to engines with seven or more cylinders, typically V8, V10 or V12 units. The ECU monitors crankshaft speed fluctuations and decides that cylinder 7 is not contributing its share of power, so combustion there is incomplete or absent. The firing order and the physical position of cylinder 7 depend on the engine, so check the manufacturer's data for the specific model.

Symptoms

Engine management light on, flashing if the misfire is severe
Rough idle and noticeable shaking
Hesitation, jerking or loss of power under acceleration
Smell of unburnt fuel from the exhaust
Increased fuel consumption
Difficult starting or occasional stalling

Possible causes

Worn, fouled or incorrectly gapped spark plug on cylinder 7likely
Faulty ignition coil or coil connector on cylinder 7likely
Faulty or blocked fuel injector on cylinder 7, or a wiring fault to itpossible
Vacuum or intake leak affecting cylinder 7, such as a damaged intake manifold gasketpossible
Low compression on cylinder 7 due to a burnt valve, worn piston rings or a head gasket leakpossible
Wiring or connector damage in the ignition or injector circuit for cylinder 7possible
Valve train problem such as a worn camshaft lobe, collapsed lifter or valve timing faultrare

How to diagnose

Read all stored codes and freeze frame data to see load, engine speed and temperature when the misfire set, and check whether other cylinders also misfire
Check the live misfire counters to confirm the misfire is limited to cylinder 7 and whether it happens at idle, under load or when cold
Inspect the coil, plug lead if fitted, connectors and wiring on cylinder 7 for damage, oil contamination, corrosion or looseness
Remove the spark plug from cylinder 7 and inspect its condition and gap, comparing it with the other cylinders
Swap the coil, and if needed the plug, with a known good cylinder, clear the codes and see whether the misfire follows the part
Test the injector on cylinder 7 for resistance, electrical signal and correct operation, and check fuel pressure
Smoke test or inspect the intake system for leaks near cylinder 7 and check for vacuum leaks
Carry out a compression test and, if needed, a cylinder leak-down test on cylinder 7, then check valve timing and valve train condition

How to fix

Replace worn or fouled spark plugs, ideally as a full set, using the correct type and gap for the engine
Replace the faulty ignition coil on cylinder 7 and repair any damaged connector
Clean or replace the faulty fuel injector and repair any wiring fault in its circuit
Repair intake leaks by replacing faulty gaskets, hoses or seals
Repair the mechanical fault found, such as valve, piston ring, head gasket or valve train repairs, if compression or leak-down tests are poor

Can I keep driving?

High severity

Avoid driving if the engine management light is flashing or the engine runs badly, as unburnt fuel can overheat and damage the catalytic converter. If the misfire is mild and the light is steady, drive gently and a short distance only to get it repaired.

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