o2 sensor, the french touch

[jcnappee]

hello again guys !
I take a look on many threads and did not find my answer.
I have a 95/03 fzj 80.
It was modified to run on sand and desert.
the catalytic(s) converter(s) have benne removed.
I have a simple question : I have only ONE o2 sensor, just befeore the pie replacing the catalytic(s) converter(s) - I put s between () because I don't know if the truck had one or two catalytics converters before modifications.
I have many problems seeming coming from the o2 sensor and I don't find the reference for a single 02 sensor, only for right and left. I don't understand how the truck can correctly run if they supressed one of the 2 orogonal o2 sensor because I think each o2 sensor is configured to analyse the exhaust gas of only three cylinders and not six !
Thanks for help and thousands apologizes for my bad language !

 

[landtoy80]

Bonjour Monsieur

Have you tried unplugging the O2 and see how it runs?
Not sure on a 95 but my 94 ran fine for about a year with the O2's unplugged. New O2's one seamed to make it idle better. The US 94 has two O2's before the cats and the cats are side by side. Newer US 80's have 2 cats inline with two O2's before and after the cats.

Is there a sticker under the hood with emissions parts on it?

You can see the O2 in front and rear of the cats on first pic newer FZJ80 . 2nd pic shows O2 only in front of cats 94 FZJ80.

If you had 2 O2's there should be a second set of O2 wires under the vehicle somewhere. My 2 sets of O2 wires run over the transmission where the engine and trans bolt up. Then goes to the wiring harness under the intake manifold.

Au revoir

 

[Timpanogos Slim]

Pre-catalyst o2 sensors are used to determine the correct fuel mixture. If the o2 sensors are missing, the ecu reverts to a "safe" operating program which likely gives lower performance and mileage.

The 2nd o2 sensor on a US '94 is much harder to see (and to remove) than the 2nd one.

 

[landtoy80]

The 2nd o2 sensor on a US '94 is much harder to see (and to remove) than the 2nd one.

What???

 

[Timpanogos Slim]

What???

The outer O2 sensor is visible just by kneeling down beside the truck.

The inner one, well, easier to see if you stick your head under. It angles toward the center of the truck.

 

[jcnappee]

Thanks for answers,
My 80 is an obd-I truck and have only one o2 sensor. I will try unplug it and come back to report. My problem is to find the good reference to replace my actual o2. I did not think to look at this detail when I bought my truck and the seller does not know himself what to answer because he did not do this modification.

 

[Timpanogos Slim]

My '94 is OBD1 as well - it has one o2 sensor for cylinders 1-3 and one o2 sensor for cylinders 4-6.

Does your truck have the PAIR system that was fitted to USA version OBD-1 FZJ80? There would be a hose and a box coming out of the front of your air cleaner housing. And then a bunch of stuff bolted to the exhaust manifold.

 

[jcnappee]

I've no pair system coming out of the front of my air cleaner box, and on the exhaust manifold I can see the place for two sensors (o2 ?) but they are original blocked.
here is a pic of my firts modification I had already unmount because the twister died (the air cleaner fibers were broken I suppose because of the mass of air running through it) :

 

[CruiseOrlando]

Those block offs on the exhaust manifold are from the PAIR system, not O2 sensors. Although you can relocate the sensors to that location if you wanted to. Where you want to be looking is under the passenger side of the truck. Follow the exhaust down until it's past the firewall area. Then you should see either the O2 sensor connectors or the sensors plugged into the exhaust. The plugs are only so long, so if they're going to be somewhere, it'd be right about that location.

 

[bonze]

Pre-catalyst o2 sensors are used to determine the correct fuel mixture. If the o2 sensors are missing, the ecu reverts to a "safe" operating program which likely gives lower performance and mileage.

The 2nd o2 sensor on a US '94 is much harder to see (and to remove) than the 2nd one.

Don't mean to high-jack this thread... But it's really interesting because my O2 sensors coded in my LX 450 and were determined to be bad(I did not replace them), but my gas mileage went up..from 10-12 mpg to 17-17.5 mpg. I did add Lucas oil every 3 fill-ups and premium (ethanol) gas, but even before adding the Lucas I noticed a smoother running truck. I've read where others experienced a smoother running 80 after an O2 sensor was un-plugged. Does anyone know if it's safe to leave the 80 in the "safe" mode? or explain the improvement in performance?

 

[landtoy80]

I ran without O2 for many thousands of miles with no ill affect.

A bad or weak O2 will cause negative affect. Rough idle and eventually cause the motor to stumble and not run. I played with my O2 for a couple years unplugging them then months later plugging them back in. Its strange,I would get a CEL code for bad O2, unplug them and later plug them back in and would get no code for months.

I am not sure if the increase in mileage is from going from a weak O2 to running in safe mode or if the motor just like to run on safe mode. I plan on unplugging them after I get a baseline mpg after doing a tune up and adjusting all that needs adjusting; TPS, transmission cable, throttle cable, make sure there are no vacuum leaks from old hard dry vacuum hoses.

 

[jcnappee]

Those block offs on the exhaust manifold are from the PAIR system, not O2 sensors. Although you can relocate the sensors to that location if you wanted to. Where you want to be looking is under the passenger side of the truck. Follow the exhaust down until it's past the firewall area. Then you should see either the O2 sensor connectors or the sensors plugged into the exhaust. The plugs are only so long, so if they're going to be somewhere, it'd be right about that location.

I already know that my friend, but my problem is that I noticed I have only one o2 sensor and not 2.

 

[landtoy80]

You need to get a factory service manual or a schematic on your wiring from a Toyota parts dealer that is for your make of Land Cruiser and looks to see if you have one or two O2's.
I would assume that the person that installed the exhaust, would just leave the wiring to the second O2 (if there is one) intact. So if there was a second O2, the wiring and plug should still be under the vehicle somewhere. Look in the areas from both pic I posted and see if you see an unplugged connector or cut set of wires.

Is the check engine light on all the time?

If one O2 is unplugged, you should have the check engine light (CEL) on. IF you turn the key on without the motor running, the check engine light should light up. If it doesn't then one of two things are happening, either the bulb is burnt out/removed or your vehicle doesn't have one.

If your check engine light does light up when you turn on the key and when you first start the engine and then turn off, you should be able to run a check to see if you have a second O2.
With the motor running, see if the check engine light is on. Turn off motor, unplug the O2 and see if the light comes on. You might have to drive around to get the light to turn on. If you don't get a check engine light until you unplug the O2, then you only have one O2.

Try this:

1) Does your check engine light work? Yes No
Yes, go to 3)
No, go to 2)

2) Replace bulb and turn on key to see if it lights up again. Does it light up? Yes No
Yes, go to 3)
No, you dont have a check engine light on your model or its defective

3)Is the check engine light on all the time when engine is running? Yes No
Yes, check for an engine fault code
No, go to 4)

4) Unplug the O2. Does the check engine light come on right a way or after driving? Yes No
Yes, most likely you only have one O2
No, your motor doesn't monitor O2 sensors or your computer is defective and doesn't record a fault code

 

[jcnappee]

Thanks for this step by step walkthrough. I try it and come back to you. I ve already the epc diagram. It shows 2 o2 sensors onthe pic but say one in the list of reference...

 

[CruiseOrlando]

Would it be possible that this particular truck was delivered without both sensors?

The plug should still be there regardless. Just a thought.

 

[jcnappee]

So I realised the test as described above. I disconnected the o2 and it ran normally. Perhaps just less powerfull. In fact I suspect the o2 or the harness connected to the o2 encounting problems because my truck regularly is in lack of power then have back suddenly more power as if there was an electrical malfunction. When o2 is disconnected, the truck seems working with less power. But even with my o2 disconnected, the check engine does not light during running. I hope my bad english is not so hard to understand.

 

[Timpanogos Slim]

Check the wiring harness on the exhaust side of the engine compartment where it runs near the EGR tube.

 

[jcnappee]

Already done. My egr is disconnected. The harness is not burned lol...

 

[landtoy80]

Did you get the check engine light to turn on at startup or with the key on but motor not running?
Have you checked for engine codes?

Is your motor a OBD1 or OBD2? On board diagnostics is what OBD stands for.

That is do you have what is in 1st pic on the firewall under hood?

Or do you have a plug port like on the top of this pic somewhere on the driver side in side the vehicle. Someone correct me if the pic of the OBD2 post is worng, I have never seen a OBD2 on a LC.

If its a OBD1 you can check engine codes your self without a scanner. If you have OBD2 then you can use a scanner.

 

[jcnappee]

My truck is obd 1 and I ve no check engine code when using my key to check it