UofODucks

Well, I must say this forum has proven to be very valuable. I just bought a 2000 RX300 from a friend. It has been well maintained and serviced at the dealer for most of the 196000 miles. A couple weeks ago it was showing cel 0350. After reviewing different threads associated with this, I replaced the A/F sensor, on the b1s1 side (back of motor) by firewall. I did use factory parts ( Denso 345-9009 ). Removed the battery cable to reset the computer. I also replaced the air filter to a K&N filter in the stock air box. I drove perfect around town for 2 days. Bought up to running temp with no issues. Then I took it on the Interstate for a 4 1/2 hr, 265 mile trip to WV. Still no issues. 2 days a couple hundred miles... No issues. Went to work day three my problems started to return. Hesitation at first, then hestation and sputtering. No CEL at this point. Started home and the OD would not kick in. The CEL started flashing, I was in the woods no chance to get it checked. Had to get back to the hotel so I pulled the battery cable. Waited 10 min. Hit the road with no issues. This morning it still sputters and hesitates, but no CEL. Please help. I got the RX300 cheap because my friend was afraid it needed a transmission because of the OD issue. I am hoping that is not the case.