P0308 Cylinder 8 Misfire Detected

P0308 indicates a detected misfire on cylinder 8. The affected cylinder is known, but the failed system still needs to be proven.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not clear repeated cylinder 8 misfires without repair; recurring misfire can damage the catalyst and mask mechanical faults.

Symptoms of P0308

Rough idle or a distinct shake, often worse at low RPM.
A stumble or dead spot traced to cylinder 8.
A flashing check-engine light when the misfire is active.
Slight power loss and worse fuel economy.

Common causes of P0308

A worn spark plug or failed ignition coil on cylinder 8.
A clogged, leaking, or dead injector on cylinder 8.
A vacuum leak or low compression local to that cylinder.
Carbon-tracked plug boot or damaged coil wiring.

Useful checks before replacing parts

Compare cylinder 8 contribution, misfire counters, plug condition, coil command, injector data, and compression.
Inspect local intake leaks, wiring damage, connector fit, and plug-well contamination near cylinder 8.
Review freeze-frame temperature and load to separate cold-only, idle-only, and high-load misfires.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.