P0300 Nissan Altima
Random/Multiple Cylinder Misfire Detected · Powertrain Code · High · Repair: Easy
What is P0300?
The ECM has detected misfires occurring in multiple or random cylinders. Common causes include worn spark plugs, faulty ignition coils, vacuum leaks, low fuel pressure, or a failing catalytic converter.
When the Nissan Altima triggers code P0300 (random/multiple cylinder misfire detected), it typically points to an issue in the powertrain system. This is a high severity code, so address it promptly to avoid further damage or safety concerns. Below you'll find the most common causes, symptoms, and repair options specific to the Nissan Altima.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Nissan Altima.
Common Causes on Nissan Altima
- Ignition coil failure on 2.5L QR25DE or 2.0L MR20DD four-cylinder (Altima/Sentra)
- Spark plug electrode wear on QR25DE causing weak ignition at high mileage
- Carbon buildup on intake valves from direct injection on MR20DD engine (2020+ Sentra)
- Catalytic converter heat soak damaging nearby ignition components on 2.5L Altima
- Vacuum leak at intake manifold gasket or PCV hose on QR25DE engine
Symptoms
- Rough idle with noticeable engine vibration
- Engine shaking or stumbling under load
- Loss of power during acceleration
- Check engine light flashing intermittently
- Poor fuel economy
- Hesitation or stumble on acceleration
Notes for Nissan Altima
The QR25DE is a reliable engine but ignition coils are a common wear item beyond 80k miles.