my 94 sc300 is getting a rattling noise from the motor but only when im accelerating and its more noticeabe when its hot outside and i have the ac running.. anyone have this happend?

 

My serpentine belt pulley / tensioner is doing this. It sounds like rocks are scrambling around at certain times. Replacing the pulley bearing should correct it. If you are listening in the engine bay and put your ear close to the serpentine belt pulley and blip the throttle you may hear the noise in the front of the motor.

 

when the tensioner is bad, your gonna hear a clicking noise coming from the from of the motor, almost sounds as if the fan is scraping something. If your going to replace the tensioner, its a good idea to do the timing belt an water pump also since your gonna have access to it