P0307

Code

Generic P — Powertrain

Cylinder 7 Misfire Detected

Brand: Generic

Type: P — Powertrain

Views: UK: 41 EN: 47 RU: 38

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty or fouled spark plug in cylinder 7
Failed or weak ignition coil (coil-on-plug) for cylinder 7
Clogged or failed fuel injector on cylinder 7
Low cylinder compression (worn piston rings, burned valve, head gasket)
Intake manifold vacuum leak or intake gasket leak near cylinder 7
Low fuel pressure or weak fuel pump

Symptoms

Check engine light (MIL) illuminated
Rough idle or vibration at idle
Loss of power and hesitation under load
Reduced fuel economy
Increased exhaust emissions and possible rotten-egg smell if catalytic affected
Occasional hard starting or stalling

What to check

Read and record all stored/PENDING codes and freeze-frame data with a scan tool
Check misfire counts and identify whether misfire is isolated to cylinder 7 or intermittent
Visual inspection: wiring, connectors, coil-on-plug boots, and spark plug for cylinder 7
Swap ignition coil from cylinder 7 with a known-good cylinder to see if misfire follows the coil
Swap fuel injector (or swap injector harness/connector) with another cylinder to see if misfire follows the injector
Check fuel rail pressure with a gauge to confirm system pressure within spec

Signal parameters

Misfire count for cylinder 7 (events/cycle or per minute)
Short-term fuel trim (STFT) and long-term fuel trim (LTFT) (%)—look for large corrections on the affected bank
Injector pulse width (ms) for cylinder 7
Ignition coil primary resistance (ohms) and secondary resistance (kΩ) or coil dwell time (ms)
Fuel rail pressure (psi / bar) at idle and under load
Crankshaft/Camshaft position sensor signals and cam/crank correlation (timing)

Diagnostic algorithm

Read and record all DTCs and freeze-frame data; note operating conditions when P0307 set.
Confirm misfire is current: monitor live misfire counters and identify if it's steady, intermittent, or load-dependent.
Perform visual inspection of spark plug, coil, boot and wiring for cylinder 7; replace or re-seat if damaged.
Swap the ignition coil from cylinder 7 with a known-good cylinder. If misfire moves, replace the coil.
If coil swap is negative, swap the injector (or its connector) with another cylinder. If misfire follows, replace the injector.
Check fuel rail pressure and ensure regulator and pump are within spec; inspect fuel filter if applicable.

Likely causes

Worn, fouled or incorrectly gapped spark plug in cylinder 7
Failed ignition coil for cylinder 7 (common on coil-on-plug systems)
Stuck/failed fuel injector or poor injector spray pattern for cylinder 7
Low compression on cylinder 7 (mechanical issue)
Damaged wiring or loose connector to coil/injector on cylinder 7

Fault status

⚠️ Status

Engine control detected a misfire specific to cylinder 7. MIL set; increased emissions risk and potential catalytic converter damage if unresolved. Further testing required to identify cause (ignition, fuel, mechanical, or wiring).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours

Repair manuals