Q60 Red Sport Misfire - P030x Codes & Rough Idle

ClearTheCode admin answer:

Experiencing P0301 and P0303 misfire codes on your 2017 Infiniti Q60 Red Sport 400 at 65,000 miles is not uncommon, especially with the high-performance VR30DDTT engine. Misfires can be caused by several factors, but ignition components (spark plugs and coils) are often the primary suspects.

Here's a breakdown of common causes and diagnostic steps:

Common Causes of Misfires (P030x codes):

1. Spark Plugs: Worn or fouled spark plugs are a very common cause. The VR30DDTT engine, being twin-turbocharged, puts more stress on ignition components. Infiniti often recommends spark plug replacement around 60,000 miles for these engines.
2. Ignition Coils: A failing ignition coil can lead to a lack of spark in a specific cylinder. They can degrade over time, especially with heat cycles.
3. Fuel Injectors: A clogged or faulty fuel injector can prevent the cylinder from receiving enough fuel, leading to a lean misfire.
4. Vacuum Leaks: Leaks in the intake system can cause unmetered air to enter, disrupting the air-fuel ratio and leading to misfires.
5. Compression Issues: Less common, but low compression in a cylinder (due to worn piston rings, valves, or head gasket) will cause a misfire.

Diagnostic Steps for P0301, P0303:

• Swap Test (Coils): The easiest way to diagnose if it's an ignition coil is to swap the coil from cylinder 1 to a known good cylinder (e.g., cylinder 2 or 4) and the coil from cylinder 3 to another good cylinder. Clear the codes, drive the car, and re-scan. If the misfire codes follow the coils (e.g., you now get P0302 and P0304), then the coils are faulty.
• Swap Test (Spark Plugs): If swapping coils doesn't change the misfire location, you can try swapping the spark plugs in the same manner. If the misfire follows the plug, replace the plug.
• Inspect Spark Plugs: When you remove the plugs, inspect them for signs of fouling (oil, carbon), wear, or damage. This can provide clues about the engine's health.
• Fuel Injector Test: If coils and plugs are ruled out, a professional can test fuel injector pulse and spray pattern. You can also try adding a high-quality fuel system cleaner, though this is less effective for completely clogged injectors.
• Vacuum Leak Check: Listen for hissing sounds around the intake manifold and vacuum lines. A smoke test can precisely locate vacuum leaks.

Parts Recommendations:

• For spark plugs and ignition coils on a Red Sport, it's highly recommended to use OEM Infiniti/Nissan parts or high-quality aftermarket equivalents (e.g., NGK, Denso) specifically designed for the VR30DDTT engine. Using incorrect or cheap parts can lead to further issues.

When to see a shop:

• If your diagnostic steps (swapping coils/plugs) don't pinpoint the issue.
• If you suspect a fuel injector problem or a vacuum leak that you can't locate.
• If the misfire is accompanied by other symptoms like excessive smoke from the exhaust, coolant loss, or unusual noises, which could indicate a more serious internal engine problem.
• Driving with a persistent misfire can damage your catalytic converters (which are expensive to replace), so address it promptly.