ihave engine code po170 fuel trim malfunction bank1 on 1995 Lexus ES300

the car is hard to start but once sarted runs fine

Asked by for the 1995 Lexus ES300
That code on other year Lexus is usually caused by a dirty or failing air flow meter but not really common on the air flow meter on your car. You could try cleaning the throttle housing with chemtool making sure the throttle housing /butterfly are all clean, then check for vacuum leaks around the intake manifold and air filter housing to throttle housing air induction boot.
After that I would suggest perhaps the idle air control valve under the throttle housing may be dirty and stuck open. Does the engine stall after first start up or do you find you have to raise the idle by putting your foot on the accelerator when you first start the engine from cold? All signs of a dirty idle air control motor.