Your 2022 Grand Cherokee should idle like a luxury SUV—smooth and refined. When a rough idle appears with a P0300 random misfire code, something is disrupting combustion across multiple cylinders. The cause depends partly on which engine powers your Grand Cherokee.
Understanding P0300
The P0300 code indicates "Random/Multiple Cylinder Misfire Detected." Unlike cylinder-specific codes, random misfires suggest a systemic issue affecting all cylinders—fuel delivery, air supply, or common ignition components.
2022 Grand Cherokee Engines
The 2022 Grand Cherokee offers multiple powerplants:
- 3.6L Pentastar V6 - Most common, known for some specific issues
- 5.7L Hemi V8 - More cylinders, more potential misfire sources
- 4xe Plug-in Hybrid - Additional electrical considerations
Symptoms
- Engine shaking at idle
- Check engine light (may flash if severe)
- Hesitation during acceleration
- Decreased fuel economy
- Rough running through the RPM range
Common Causes - Pentastar 3.6L
- Rocker arm/lifter issues - Known Pentastar problem
- Ignition coil failure - Can affect multiple cylinders
- Spark plug wear - Due for replacement at 100k miles
- Intake manifold leak - Vacuum leak causing lean misfires
Common Causes - Hemi 5.7L
- Cam/lifter failure - Emerging issue on newer Hemis
- MDS system malfunction - Cylinder deactivation issues
- Ignition coil failure - 8 coils, more failure opportunities
- Exhaust manifold leak - Affects O2 sensor readings
Diagnostic Steps
- Check for additional cylinder-specific codes
- Inspect all ignition coils and spark plugs
- Listen for valve train noise (lifter issues)
- Check for intake or exhaust leaks
- Monitor fuel trim data
Repair Costs
- Spark plugs (V6): $150-$300
- Spark plugs (V8): $200-$400
- Ignition coil (each): $75-$175
- Rocker arm/lifter repair: $1,500-$4,000