Nissan Murano P0300: Random or Multiple Cylinder Misfire Detected

Nissan Murano P0300 Random Misfire Diagnosis

Quick Answer: What is P0300?

On a Nissan Murano, the P0300 code triggers when the engine computer detects multiple cylinders are not firing correctly. In the 3.5L V6 engine, this is typically caused by failing ignition coils (due to heat), worn spark plugs, or a faulty crankshaft position sensor.

Severity: HIGH. If your Check Engine Light is flashing, pull over immediately. A blinking light means the misfire is severe enough to melt your catalytic converters. On a Nissan Murano, there are three converters, and replacing them can cost over $3,000.

Common Symptoms

Rough Idle: The steering wheel vibrates significantly at stoplights.
Engine Stumbling: The car feels like it's "missing" a beat during acceleration.
Flashing CEL: Blinking light under load or at highway speeds.
Poor Fuel Economy: A sudden and sharp drop in MPG.

Most Likely Causes

Failing Ignition Coils (45%): The coils on the back bank (near the firewall) get extremely hot and fail first.
Worn Spark Plugs (30%): If the Iridium plugs haven't been changed in 100k miles, the gap is too wide.
Faulty Crankshaft Sensor: A common Nissan weak point; sending incorrect timing data to the computer.
Intake Manifold Vacuum Leak: Cracked rubber boots or intake gaskets.

Detailed Repair Cost Breakdown

Estimates for Nissan Murano (3.5L V6) in the US market:

Component / Task	Aftermarket Part	OEM Hitachi/Nissan	Labor Time
Ignition Coil (Each)	$55 - $80	$120 - $160	0.5 - 2.5 hrs (Rear bank is labor-heavy)
Spark Plugs (Set of 6)	$50 - $80	$110 - $150	2.0 - 3.5 hrs

How to Fix P0300 on a Nissan Murano

1. Replace Rear Bank Components Together

On the Murano V6, the intake manifold must be removed to reach the three spark plugs and coils in the back. Because the labor is so high ($300+), do not replace just one coil. If one has failed, replace all three rear coils and all six spark plugs at the same time to avoid paying for the same job again next month.

2. Only Use Hitachi or Genuine Nissan Coils

Nissan engines are notoriously picky about ignition coils. Cheap "no-name" coils from the internet often cause the P0300 code to return within weeks. Hitachi is the original equipment manufacturer for Nissan; use them to ensure a permanent fix.

3. Inspect the Intake Boot

Check the large black rubber accordion hose between the air filter and the engine. These are famous for cracking in the folds. If air leaks in, it causes a "lean misfire." This is a very common $60 DIY fix that solves many random misfire codes on the Murano.