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Thread: Conformation on o2 sensors?

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    Forum User Feedback Score 0 gsxr1000k2's Avatar
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    Conformation on o2 sensors?

    Ok... So the GTO failed the MOT on emissions...and I Guessed the course of action to remedy this was replace the o2 sensor.. Now having looked, I can only find one after the cat about 1/3rd way down the exhaust..Now I'm not sure if I'm right but arn't there meant to be 2-4 up in the engine bay 1-2 for each bank...as I can't find them anywhere..I even have 2nd engine stripped down and can't find where they would bolt in to the exhausts on that either..

    My GTO is H(90) JDM Import

    If anyone can put on the right path would be greatful...

    P.s Is there anything else other than the sensor that would help the car fail the emissions test..


    Cheers

    Col

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    Im not sure how emissions are done in the UK, but did you get a print out saying why you failed? do you have exhaust numbers or something?

    Also what year/model is your car? my 1993 naturally aspirated only has one O2 sensor like you describe. And before your replace a 100 dollar sensor make sure you test it, ill edit/reply with a link in a minute.

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    Forum User Feedback Score 0 paul_666's Avatar
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    Wow, quite bad for a 1990 to fail emissions!

    There is only one sensor in the GTO and it should be in the downpipe just before the CAT - it should be on the top. The 3000GT in the UK has 2 sensors mounted in the pre-cats. There should be a print out to show why it failed and from that you can normally diagnose if the cat is shot (acutally pre mid 1992 cars do not require a cat to pass) or the o2s are flatlining

    Cheers

    Paul

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    Okay, this was taken of the test report...



    DESCRIPTION LIMITS READING

    Fast Idle test:Fail

    Engine speed 2450-2850 rpm -- Not checked
    CO Max 0.30% 0.63% fail
    HC Max 200ppm 29ppm pass
    Lambda 0.97-1.03 1.02 pass


    second fast idle test:Fail

    Engine speed 2450-2850 rpm -- Not checked
    CO Max 0.30% 0.64% fail
    HC Max 200ppm 24ppm pass
    Lambda 0.97-1.03 1.01 pass


    Natural Idle:Pass

    Engine speed 550-850 rpm -- Not checked
    CO Max 0.50% 0.49% Pass



    Not quite sure where to go from here other than to replace the O2 sensor and see if there is any difference...

    I have heard that if the sensor is replaced that the ECU has relearn for a while is this right?


    Thanks for all the help..
    Current Vehicles:
    1990 GTO TT AWD AWS JDM
    1990 MK3 TT Supra JDM Roadster
    Volvo C70
    GSXR1000K2

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    Forum User Feedback Score 0 paul_666's Avatar
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    Quick refresher for troubleshooing...

    Basic fault finding for advanced emission test failures:

    1. If a vehicle fails for high CO at idle and /or fast idle then.... if
    Lambda is too low, the mixture is too rich. This can be caused either by a
    misfire or by a faulty Lambda sensor. If it's running very rich, the 02 and
    HC will be higher than normal.


    2. if it has a high Lambda and high 02 (0.5 to 1.5%), the "CAT" could be
    faulty. Before condemning it make sure its hot enough to work, the Lambda
    and other sensors are working OK and the exhaust downpipe hasn't got any
    leaks.

    3. if the vehicle fails for high HC then ...if the CO passes, the vehicle
    is probably misfiring. Or if the CO fails and the Lambda reading is too low,
    the mixture is probably too rich and it may also be misfiring.

    4. if the CO fails, the Lambda reading is high and the O2 reading is high
    (0.5 to 1.5%) the "CAT" could be faulty. Again check out the simple measures
    above before condemning it.

    5. if the Lambda fails then...if its too high the Lambda sensor may be
    faulty, the mixture may be too weak or there may be a hole in the exhaust
    downpipe. If Lambda is too low the sensor may be faulty, the mixture may be
    rich or the vehicle may be misfiring.

    Looks like No.1 to me, if the o2 sensor is flatlining it will prob show as lean so the engine is over compensating

    If you have anything to log it with it will show the o2 sensor output and it probably isnt functioning. Both mine were dead - replaced them both and runs much better at idle

    Yes, they ECU will have to re-learn the new sensors, just leave the batt off for five mins, put it back on and turn off the the heater and go for a drive

    Hope that helps

    Paul

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    Forum User Feedback Score 0 paul_666's Avatar
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    Oh, and this might help -

    http://www.evilempireperformance.co....products_id=76

    Rob is in the UK and its worth a call to him to confirm the exact O2 sensor - think there are three to choose from (he can check off your VIN)

    Cheers

    Paul

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    Forum User Feedback Score 0 enigma's Avatar
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    If you car is registered before august 1992 it should only have a basic idle test, not the fast idle test! also the cat is not a mandatory requirement on the pre 92 test vehicle.

    Tony

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    Forum User Feedback Score 0 gsxr1000k2's Avatar
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    Quote Originally Posted by paul_666 View Post
    Oh, and this might help -

    http://www.evilempireperformance.co....products_id=76

    Rob is in the UK and its worth a call to him to confirm the exact O2 sensor - think there are three to choose from (he can check off your VIN)




    Paul
    Thanks for that... have already installed a new O2 sensor..but could only find one...thanks for letting me know about the ecu relearning..will do that..

    Cheers

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    Quote Originally Posted by enigma View Post
    If you car is registered before august 1992 it should only have a basic idle test, not the fast idle test! also the cat is not a mandatory requirement on the pre 92 test vehicle.

    Tony
    Thanks...If you mean the natural idle test....that figures, as thats the one it did pass on...

    May mention that whenn i take it back..

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