Mechanics

HELP WITH OXYGEN SENSOR READING

2000 Lexus LS 400

Computer problem
2000 Lexus LS 400 V8 Two Wheel Drive Automatic

Need help with O2 sensor readings.

I have LS400 2000 model which has 4 Oxygen Sensors.
I think that i may have some problem in my O2 sensors.
if you guys could check this readings and help me with this issue & tell me if these sensors are either functioning correctly or not.

These are readings of O2 sensor on idle without acceleration.
http://www.mypicx.com/uploadimg/930206311_09092010_1.gif

These are readings of O2 sensor with accelerate up to 2000 rpm.
http://www.mypicx.com/uploadimg/1865280210_09092010_2.jpg

These are readings of O2 sensor back on idle without acceleration.
http://www.mypicx.com/uploadimg/396716114_09092010_3.jpg

These are readings of O2 sensor again with accelerate up to 2000 rpm.
http://www.mypicx.com/uploadimg/1538730705_09092010_4.jpg


These are readings of O2 sensor back finally on idle without acceleration.
http://www.mypicx.com/uploadimg/80784772_09092010_5.jpg

I do not have any DTC
http://img842.imageshack.us/img842/8947/dtcevap.jpg

the only problem is that
fuel mileage is low which is 19 - 20 MPG on highway compared with other LS400 owners who get 24-30 MPG on highway.
I have changed spark plugs, cleaned engine air filter. But i think it may be because of these O2 sensors.

Bank 1 sensor 2 readings are not similar to Bank 2 sensor 2 readings, does this means that i had to replace the sensor.

these are Fuel system data
http://www.mypicx.com/uploadimg/2091564011_09092010_1.jpg

Live data at idle without acceleration
http://www.mypicx.com/uploadimg/1007021370_09092010_2.png

Live data with acceleration on 2000 rpm
http://www.mypicx.com/uploadimg/1688292499_09092010_3.png

DTC at mode 7 , no pending DTC
http://www.mypicx.com/uploadimg/1656117433_09092010_5.png

Monitored Test Results
http://www.mypicx.com/uploadimg/472242860_09092010_4.png

I don't know about these readings, could you tell me in case if any of these readings are wrong..
Avatar
Qewani
September 22, 2010.



Is there a way for you to get bank 1 sesnor 2. And short fuel trim bank 1 over top of eachother.

And the same with bank 2 sensor 2 and short term fuel bank 2 over top of eachother like you did with o2 sensor 1 and 2 on each bank?

Blackop555
Sep 27, 2010.
Also can you get more info to show up on the graph from idle to acceleration and then let go back to idle. About maybe 5 seconds idle to accel then back to idle. That would be great

would like to see the o2's on eachother. Then each bank o2 sensor and their fuel trims.

Too inconclusive right now since I dont have the fuel trims with the o2 sensors to see whats going on right now. If you cant get any more info I can give you a good guess but with that little info ill be a lot more precise

Blackop555
Sep 27, 2010.
Here are data which you have requested.

on idle
http://img801.imageshack.us/img801/5647/idlinghere1.jpg

on accelerate for 5 seconds
http://img812.imageshack.us/img812/9414/acc5seconds.jpg

then back to idle
http://img826.imageshack.us/img826/1392/back2idlelast.jpg

waiting for your reply.
thanks.

Tiny
Qewani
Sep 28, 2010.
Last thing is switch the o2 sensors around and see if the graphs change with them or if the different o2 from the other bank still shows that big flatline on the bottom when your hit the gas like that. Can you get a graph of the fuel trims and the bank 2 sensors when you hit the gas to the floor for a split second?

Blackop555
Sep 28, 2010.
I did not switch the o2 sensors around yet. if you want me to do this inform me.

this is the graph of the fuel trims and the bank 2 sensors when i hit the gas to the floor for a split second.
http://img299.imageshack.us/img299/4452/bank2withslipt.jpg

this is the graph of the fuel trims and the bank 1 sensors when i hit the gas to the floor for a split second.
http://img178.imageshack.us/img178/2295/bank1withslipt.jpg

this is some live data
http://img683.imageshack.us/img683/3043/livedata.jpg

inform me if you need any other/extra readings.
Thanks.

Tiny
Qewani
Sep 29, 2010.
Looks like your having a issue with lack of fuel. Maybe dirty injectors or low fuel pressure. When you hit throttle they shoudl show rich but instead they are showing lean.

Your long terms are pretty high indicating adding more fuel which could result from a bad fuel pump or dirty injectors.

Reset the KAM and go from there. After its reset re run it and pay attentinon.

If the shorts and long terms start to raise right away bring vehicle off of idle and see if the fuel trims start to come back down untill it idles again. If so its a vaccuum leak.

If not it could be a dirty maf, plugged injectors, or low fuel pressure

Blackop555
Sep 29, 2010.
From your previous post I could not understand this sentence
>>
if the shorts and long terms start to raise right away bring vehicle off of idle and see if the fuel trims start to come back down until it idles again.
<<

Can you explain more how to preform this?

I want to tell you that there is small crack on the hose called "PS Air Hose"
Could this be the vacuum leak?

Tiny
Qewani
Sep 30, 2010.
If short and long term fuel trim raise up as in leave 0 up to 5, 6, 7 8 percent etc and keep raising raise vehicle off of idle and see if the fuel trims drop back down to 0-5 percent

Blackop555
Oct 1, 2010.
I had reset the KAM and run the car and monitored STFT reading which were between 0% to -3% and LTFT reading were 12%. Both reading direct came with these values without any start from 0, 1, 2, . Etc

I found that PCV valve is very dirty/may leaking and I think it may causing the lean problem on idle. I will clean or replace it and check the STFT/LTFT readings again.

Tiny
Qewani
Oct 1, 2010.
PCV hose was cracked and leaking on both of
intake manifold side and cylinder head side.

i used a tape and installed hose back. cleared KAM and checked STFT/LTFT readings which came with these values
http://img705.imageshack.us/img705/1566/bank1withsplit.jpg
http://img412.imageshack.us/img412/9136/bank2withsplit.jpg

Tiny
Qewani
Oct 2, 2010.
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