The P0300 code in your 2018 Toyota Camry indicates random or multiple cylinder misfires detected by the powertrain control module. Unlike cylinder-specific codes (P0301-P0308), P0300 means the misfires are occurring across multiple cylinders without a consistent pattern, making diagnosis more challenging but also pointing toward system-wide causes rather than single-cylinder problems.
The 2018 Camry Engine Options
Your 2018 Camry features either the 2.5L 4-cylinder (A25A-FKS Dynamic Force) or the 3.5L V6 (2GR-FKS). Both engines use direct injection and variable valve timing. The P0300 code combined with rough idle suggests a common system affecting all cylinders rather than an individual component failure.
Common Causes Affecting All Cylinders
Fuel quality issues rank highest—contaminated or low-quality fuel affects combustion in all cylinders. Vacuum leaks create lean conditions across the engine. Failing ignition coils (though rarer in newer vehicles) can cause misfires. Carbon buildup on intake valves, common in direct injection engines, restricts airflow. MAF sensor contamination provides incorrect air mass data.
Symptoms You're Experiencing
The rough idle is the engine struggling to maintain consistent combustion. You may feel shaking or vibration at stoplights. Acceleration may feel hesitant or uneven. The check engine light is illuminated, possibly flashing if misfires are severe. Fuel economy typically decreases with misfires.
Diagnostic Approach
Using Toyota Techstream, review misfire counter data for all cylinders. If misfires are relatively even across cylinders, focus on common systems. Check for vacuum leaks using smoke testing. Inspect spark plugs for wear or deposits. Test fuel pressure and injector operation. On the 2.5L, check for intake valve carbon buildup using a borescope.