Chrysler 300 P0300: Random or Multiple Cylinder Misfire Detected
Quick Answer: What is P0300?
On a Chrysler 300, the P0300 code indicates that the computer has detected multiple cylinders are failing to ignite. In the 5.7L Hemi V8, this is often caused by worn-out spark plugs (there are 16 of them!) or a collapsed lifter. In the 3.6L Pentastar V6, it is frequently due to failed ignition coils or carbon buildup.
Common Symptoms
- Rough Idling: The heavy car shakes at stoplights.
- Lack of Power: Significant hesitation when you floor the gas pedal.
- Flashing CEL: The Check Engine Light blinks during acceleration.
- Service AWD/Traction Light: On many Chrysler 300s, the traction control system will disable itself when a misfire occurs.
Most Likely Causes
- Worn Spark Plugs (45%): The Hemi engine uses two plugs per cylinder (16 total). If one bank is old, it triggers random misfires.
- Failed Ignition Coils: Common in both V6 and V8 models as they reach 100k miles.
- Mechanical Lifter Failure: A known weak point in the 5.7L Hemi engines.
- Vacuum Leak: A cracked intake manifold or leaking PCV hose.
Detailed Repair Cost Breakdown
Estimates for Chrysler 300 (3.6L V6 and 5.7L V8) in the US market:
| Component / Task | Aftermarket Part | OEM Mopar Part | Labor Time |
|---|---|---|---|
| Spark Plugs (Set of 16 for Hemi) | $120 - $180 | $220 - $300 | 2.0 - 3.0 hrs |
| Ignition Coil (Each) | $40 - $65 | $110 - $160 | 0.5 hr |
How to Fix P0300 on a Chrysler 300
1. Change All Spark Plugs
If you have a 5.7L Hemi, do not just change 8 plugs. There are two per cylinder. If you reach 100,000 miles, replace all 16 with Genuine Mopar or NGK Iridium plugs. This is the most common and effective fix for a random misfire on this platform.
2. The Coil Swap Diagnostic
If your scanner points to a specific cylinder (like P0305), swap the ignition coil with its neighbor. If the code changes to the new cylinder (P0306), the coil is dead. If the code stays the same, the issue is likely the spark plug or a mechanical problem in that cylinder.
3. Inspect the Intake Manifold
The 3.6L Pentastar engine uses a plastic intake manifold that can warp or leak air at the gaskets. Spray a small amount of brake cleaner around the intake ports while the car is idling. If the RPMs jump, you have found a vacuum leak that is causing your P0300 code.