Lexus rx300 - 1999

Random misfire codes are sometimes set by low fuel level and may not be currently present. Have you reset the fault? If so, has it come back? If you reset the fault and the code comes back, start with checking the coils and spark plugs for age/damage and be sure the fuel tank is at least half full, no more than 3/4 full or the readiness monitors will not run to completion.