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Discussion Starter #1
This is something I haven't seen much about on the forums. Another thread joged my memory to ask this.

How long do the O2 sensors (I believe there are 2, one in the downpipe and one somewhere else) on the Supra Turbo last?

WHere is the 1st O2 sensor located and what are the signs that it (and or the second one in the downpipe) is failing? I am pretty sure my car runs rich , maybe too rich according to the smell of the exhaust. I have a '94TT BPU and my car has a more intense smell than my friends '97TT BPU. I know that is a very basic way to tell, but I am wondering.

Oh yeah, my car has about 73,600 miles on it.
 

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you car has only one o2 sensor located near the cat.

you should replace them every tune up or every 60,000 miles
i belive is the correct time to change them!
 

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So what kind of sensor do I have just after turbo and what kind of sensor is in DP?

Mervinn - what boost do you have?
 

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Discussion Starter #5
I usally run around with a peak of 1.2 kgm/cm2 of boost. Right now I have my high flow cat in so i am only hitting 1.0 kgm/cm2.
 

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If you are really sure of that you are runing rich than changing O2 sensor is good idea but before that I would check out for 100% if you are runing rich. Dyno????
 

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Discussion Starter #7
I am not really sure.. all I am going by is the smell and my cars seems a little down on power compared to my firends with almost identical mods.

I am still also trying to find out if the car ('94TT) has one or two 02 sensors. I bet they are not cheap either. Probably couldn't hurt to switch them like you said.
 

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I think we have two O2 sensors but I am not sure. One is just after turbo and another is in DP. Unfortunately I am not an expert and don't know it for 100%:(
 

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All supras have 2 o2 sensors. www.sidwin.com/supra/single you can see pics of my supra and my o2 sensor right after the turbo. On stock twins the first o2 sensor is right after the turbo and in the dp. That is why obd2 cars have the check engine light blinking because you can't hook up the first o2. you have to get a high flow car.
 

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Discussion Starter #10
Ok, so a bit of conflicting info here.

Basically I want to know if there is anyway to tell if the 02 sensor(s) have gone bad on my car. Will it ever get to a point that i get check engine lights because of it? Or is it as Ranger said, replace for maintenance at 60,000 miles? Say it is time to replace, do i replace both? Remember I have an OBDI car. Also, about how much will it cost me to buy these puppies if you know?
 

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So, for what purpose is second O2 senor in 94 Supras?
 

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Yes, there are two O2 sensors on the 94. I paid $105 I think for each before I learned that the second O2 on OBDI cars has no significant function. My guess is that it was incorporated into the design of the system in preparation of OBDII. Manufacturers new well in advance of OBDII requirements and when they were coming. One which was monitoring the efficeincy of the cat, by placing an O2 before and after.

My recommendation is to treat it like a maintenance item and 60K sounds good. The first O2 is the main control item for setting your air fuel ratio. If it's out of whack or clogged then your fuel will be off.

I read once of a way to test them but it wasn't worth the effort. I can only remember it was somewhat complicated. You won't get a code unless it fails completely on OBDI.
 

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Discussion Starter #14
Thanks alot for the response. So looks like it is worth a shot to replace the first 02 sensor.
 

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This might make no sense at all. But it the car uses two O2 sensors and if they are both the same you might be able to swap them. The ones after the cats would be fresher I assume.
 
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The rear sensor is used to check the function of the cats (that's why OBDii cars have to put in a sensor simulator when no cats are used), I'm told. It doesn't tune the car like the front sensor does.

Jeff
 

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Great,
for what purpose second O2 sensor is, in 93-95 Supras?
 

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I looked at the front and rear O2s last night. They look identical with the exception of the length of the wiring harness. i would guess you could splice in to lengthen it and use it up front.

My thoughts on the second O2 are above. For three years now I have found no reference to whether the second O2 controls anything on OBDI. Again, it was probably incorporated into the design of the ecu for preparation of OBDII arrival.
 

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Discussion Starter #20
Supra400hptt... where exactly is the first 02 sensor located? Is it way up right near the turbos?
 
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