O2 Sensor Help!

[Atroop]

Hello All, I am in need of some good advise on a problem I'm having with my '99 RX300, 93,000 miles. A while back my RX was running like crap and I was getting a flashing check engine light. The codes I was getting were bank 1 random misfire and bank 1 running lean. After about a month of troubleshooting, I finally figured out that it was the Bank 1, O2 Sensor #1 (air/fuel sensor). The sensor was bad and it was giving a false lean reading to the engine, causing the injectors to shoot too much fuel into the cylinders and thus causing misfires. I replaced the sensor and since then the car has been running great.

After replacing the Bank 1, O2 Sensor #1, I started to get another check engine light reading P0136 (Bank 1, O2 Sensor #2), although the car is still running good. My question is in regards to what could be causing this as I've heard that this sensor should last for 200,000+ miles. Could my catalytic converter have been damaged when I was getting random misfires and the false lean reading by shooting hot fuel into the cat? Or could the sensor be legitimatly bad? I bought a new sensor but the old nuts are so rusted on that I can't get them off. If I cut the bolts I won't be able to get the new senor on. Any advise is greatly appreciated! Ryan

PS - I'm in the Army and leaving for Iraq in two weeks and want this fixed for my wife before I leave.

[chubyball]

Hello All, I am in need of some good advise on a problem I'm having with my '99 RX300, 93,000 miles. A while back my RX was running like crap and I was getting a flashing check engine light. The codes I was getting were bank 1 random misfire and bank 1 running lean. After about a month of troubleshooting, I finally figured out that it was the Bank 1, O2 Sensor #1 (air/fuel sensor). The sensor was bad and it was giving a false lean reading to the engine, causing the injectors to shoot too much fuel into the cylinders and thus causing misfires. I replaced the sensor and since then the car has been running great.

After replacing the Bank 1, O2 Sensor #1, I started to get another check engine light reading P0136 (Bank 1, O2 Sensor #2), although the car is still running good. My question is in regards to what could be causing this as I've heard that this sensor should last for 200,000+ miles. Could my catalytic converter have been damaged when I was getting random misfires and the false lean reading by shooting hot fuel into the cat? Or could the sensor be legitimatly bad? I bought a new sensor but the old nuts are so rusted on that I can't get them off. If I cut the bolts I won't be able to get the new senor on. Any advise is greatly appreciated! Ryan

PS - I'm in the Army and leaving for Iraq in two weeks and want this fixed for my wife before I leave.

I had the same problem I did swap the sensor left to right and right to left to see the damn codes changed, but after replaced both catalitics cost me a fortune, I end up replace the second cat with after market part with cost of $300.00 and the code still there. Finally I replace both send sensors after the cats. Now the Engine code went a way, it has not came back since. My suggestion to you is replaced both of them and reset your computer. Remember to buy Denso parts, you can purchase from the website, it's a little cheaper from dealer about $20.00 for each.

By the way, my sensor went bad at 115K miles, not at 200k

[lenore]

Ok I am confused, You changed both Oxygen sensors on the engine or did you replace the sensor down on the Catalytic converter. I believe there are a total of three sensors on the RX300?????? Two on the exhaust manifolds and one down by the Catalytic converter.

[chubyball]

Ok I am confused, You changed both Oxygen sensors on the engine or did you replace the sensor down on the Catalytic converter. I believe there are a total of three sensors on the RX300?????? Two on the exhaust manifolds and one down by the Catalytic converter.

How many cats do you have? I have a LS400 95 and it has 2 cats total of 4 Oxygen sensors, 2 before the cats (locates between manifold and cats) and 2 after the cats (locates between the cats and muffler pipe). I replace the 2 after the cats.