P1130 Lexus - Where is the air fuel ratio sensor located (bank 1,sensor 1)?

Question

I'm trying to find the location of the air/fuel ratio sensor on a '99 Lexus RX300, DTC is showing P1130(bank 1 sensor 1). Is it just another name for an O2 sensor.
I have already replaced the upstream O2 sensor but I have not done the downstream sensor next to the CAT because one of the mounting studs had been broken by someone prior to me. Is that the sensor that the code P1130 is referring to? My Haynes manual does not cover this code or this term for a sensor.
The vehicle has a substantial drive-ability problem, when cold it won't idle and stumbles badly under acceleration, after it warms up it will idle but still stumbles significantly under acceleration. This is the only DTC it has at this time but it had up to 8 DTC's when I first got it to repair.
I have also put in new spark plugs, new fuel pump & fuel filter, new PCV valve. In addition I have checked as best as I can for vacuum leaks but so far have found none.

Does anyone have any answers and/or suggestions?
Thank you.

Answer 1

The P1130 code is for the upstream (front) O2 sensor, so you did replaced the correct one. Usually a faulty O2 sensor will not cause the engine to stumble or run poorly, the cause of the problem is more than likely something else. Unfortunately there are many things that can cause that problem, do you have the list of the other codes? ignition coils or fuel injectors are common problems for those symptoms.

Comments

Thanks for the quick reply.
After some research I found out that the sensor I replaced was bank 1, sensor 2. The sensor that is faulty is on the rear side of the engine, I found out that sensor 1 is always located on the side where #1 cylinder is. On this vehicle the book showed that #1 is on the rear instead of the front, which was new to me so we are going to replace it and see how it does.
However, when I was replacing the plugs I found one coil (#4) that had some rust colored dust on it similar to what you would find in a worn dist. cap, is there a way to test it or should it be replaced? I did test it with a spark tester, it seemed OK but I'm still not sure about it.The other five coils looked pristine so I don't see a problem with them.