Engine on then off,then on and stays on. I took a reading with the code reader and it said PO171 System too LEAN (BANK 1). COULD IT BE A FUEL SENSORor the Spark plugs. The car has plenty of power.

 

MAF sensor is a possibility. A/F sensor would normally be the the case if accompanied by another code. P0171 is the most common type error on RX300s as far as cels, see this recent thread, https://www.clublexus.com/forums/sho...d.php?t=290791

Most of the time the sensors just detect a brief condition out of its ratios and it pops the light. That thread above indicates how to check the MAF and also resetting the light. Gas cap not tightened enough and a disconnected air hose to the back of the air box can also be a possibility.

 

I used the reader and it said Code 171 system on the right bank lean. Please help me.

 

I'd merge both of your threads into one. They're the same questions and the same problems.
You got a bad MAF or Mass Air flow meter. Lexmex already did the search for you and post the link.

 

You were right it was the MAF sensor. opened it up and brushed clean,and so far been good. Thank you. genijet

 

I went on Ebay and bought a MAF sensor and it looked like new. Replaced it and it works good. Carl genijet