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I have an 84 Celica Gt and i was wondering when should the o2 sensor should be replaces....i have 151 500 kms on it....thanks
 

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what does it do? have you been told to replace it? whats wrong with your enigne?

BTW you do know that this is a 79-81/82-86 "Celica Supra" forum right. But Im sure people will still help you out anyway :wink: and you might be able to get more help at www.celica.net
 

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the oxygen sensor tells the ecu if it's running rich/lean. some people put 250K miles on their car and never replace them. only thing that'll happen is the engine runs a little rich because instead of compensating for rich it sees the o2 sensor is always reading one thing or another and stops using it and goes to a fuel map. you can replace it if you want nothing will happen if you leave it alone but every 100k miles it should be replaced to keep your mileage up. basicly if you have platinum plugs you should replace it everytime you replace your plugs.
 

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i need to change mine, i know its going south, well also i have an injector leaking causing a rich condition sometimes...hard starts...blah..i'm not about to rip all that shit apart....but i would suggest that if you want to try to improve your gas milage that you replace it since your at 150k....it couldn't hurt....when they go bad all together they can cause your check engine light to come on and a rough running condition
 

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trdmkii said:
i need to change mine, i know its going south, well also i have an injector leaking causing a rich condition sometimes...hard starts...blah..i'm not about to rip all that shit apart....but i would suggest that if you want to try to improve your gas milage that you replace it since your at 150k....it couldn't hurt....when they go bad all together they can cause your check engine light to come on and a rough running condition
i was about to correct you on there but i am taking my information assuming the 5m is powered by a tccs ecu. which doesn't turn on a check engine light even if the o2 sensor is missing and won't cause a rough idle /running condition. might lose some hp but it's like 1hp-2hp.

what 5m supras used the tccs?
 

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easy enuff to find out and fix.
from 86 tsrm p. FI-62 do "check idle speed" with an analog voltmeter.
it really checks whether ox sensor is working. if bad then see pps.
FI-73 and 74 to diagnose.
 

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MA Supra's: 83 - 86 5MGE's use TCCS. 82's don't.

Not sure about MX Cressida's.
 

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This is a good time to ask for help with my problem. I have replaced everything(pump, regulator, injectors, filter, O2 sensor are all brand new)
and i still start out way rich and as i drive i lean out (sometimes i have to drive for an hour before this happens) usually it takes about 15 minutes of hyway driving) ... so bad that the engine light comes on ( I have an Autometer ratio guage)
The wierd thing is if i sit at a light for a few minutes.. it seems to fix itself.. like its cooling off.. .. I just need some ideas of where else to look.

OH, what does the vacumn hose do to the fuel pressure regulator?
 

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The vacuum line on the FPR connects to straight intake manifold vacuum which allows the FPR to lower the fuel pressure at idle. The starting off rich and then leaning out condition could be caused by your MAF sensor calibration.
 

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The TCCS ECU in the 83-86 keeps an eye on the varying feedback voltage from a normally operating 02 sensor. The problem is that the ECU is only programmed to detect when the feedback voltage is either normal and constantly varying or if the sensor output remains at a constant, non varying voltage, indicating a continuous lean signal which causes the ECU to trigger a code 21. Most of the time when the 02 sensor fails, the sensor no longer produes an output signal and the ECU isn't programmed to detect a 0 voltage signal for any length of time, thus no check engine light when the 02 sensor fails.
 

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and from my experience with my o2 sensor dying code 21 doesn't cause a check angine light either. the code was there it just never turned on the light. on the cressidas i think 83 or 85 and up got the tccs. and it sounds like one of the error codes that wouldn't trigger the light since it filters codes to the light as urgent and non-urgent...if it'll hinder driving ability or cause damage possibly it'll turn on the light.
 

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Instead of replacing an O2 sensor that may be good, buy a $30
A/F meter which is hooked up all the time and it will tell u immediately
when the O2 sensor fails which is the correct time to replace it.
 

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So if you have an Air/Fuel Ratio gauge hooked up and it just stops reading altogether, the O2 sensor has most likely failed? I'm curious because my Autometer A/F gauge has suddenly stopped working and now my car has a weird idle when coming to a stop. Any other info on this?

Thanks!
 

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i just replaced mine today and it was the original i think.... the connector was yellow.

so far i see no difference.... but my gas millage i guess will tell me later :)
 

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So if you have an Air/Fuel Ratio gauge hooked up and it just stops reading altogether, the O2 sensor has most likely failed? I'm curious because my Autometer A/F gauge has suddenly stopped working and now my car has a weird idle when coming to a stop. Any other info on this?
imo, yes and from 9 posts earlier in the thread

easy enuff to find out and fix.
from 86 tsrm p. FI-62 do "check idle speed" with an analog voltmeter.
it really checks whether ox sensor is working. if bad then see pps.
FI-73 and 74 to diagnose.
 

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ive got a quick question. i just failed emissions and have diagnosed a bad o2 sensor. i went to the auto parts store and picked one up for 40 bucks and now im looking at how it connects. the stock sensorhas a thick wire running into a bundle of wire 18 or so inches away and this new bosch sensor has a connector bit about 6-10 inches away. how should i connect them? cut off the connector and crimp them together or what?
thanks!
 
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