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o2 sensor

Discussion in 'VN - VP Holden Commodore (1988 - 1993)' started by Fully, Sep 21, 2005.

  1. Fully

    Fully New Member

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    Hey

    just wondering if with the fault codes even thought i get code 12 (system all good) could my o2 sensor still be dead or not working properly? i heard that the o2 sensor only last about 100,000 km's and my car has done almost 200,000km's? i ask this as i have poor fuel economy and want it to be an easy fix. btw my fuel economy is about 350km's to 52ltrs, 85/15 metro/highway, car is stock except for cai. been serviced regularly as my brother owned it before me.

    cheers
     
  2. s0sage

    s0sage Posting aimlessly ..

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    there is a designated fault code for your o2 sensor...
    if its not shown then its not blown

    check the other threads around here on fuel economy problems and solutions. ive posted enough about it i think ..
     
  3. Cheap6

    Cheap6 New Member

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    Absolutely the O2 sensor can be working poorly and not set a code. Conversely, just because an O2 sensor code is set, doesn't necessarily mean that the O2 sensor itself is faulty. The codes are set only because the ECM doesn't receive values within what it is programmed to accept.

    The best way to check an O2 sensor is to use an oscilloscope and plot the voltage against time and compare it with a known good curve. Given that option is probably not available, you can guess, and replace the O2 sensor anyway. It won't hurt anything and they aren't particularly expensive; about $80, I think, but it will be a guess.
     
  4. Fully

    Fully New Member

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    yeah thats wat i thought,

    i dont really have the money to go on a guess and i heard its a bitch to get the o2 sensor off, so i think i might just do a service and tune and then look at my injectors!!!!

    cheers
     
  5. BR377

    BR377 Guest

    Pull it out and have a look at it :)
    Mine doesn't exist anymore, well the bit that goes inside is completely burnt or corroded away and it does nothing accept plug a hole in my manifold hehe...
    I think i'll replace it soon, i get under 300km to a tank!
     
  6. samuels

    samuels Active Member

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    the last time i quoted an O2 sensor was around the $120.00 mark,but of course thats retail :)
     
  7. samuels

    samuels Active Member

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    O2 sensor has nothing to do with your fuel economy :)
    naturally depending on the amount of work you have done to your motor(worked) these may not totally comply for obvious reasons.
    but for a standard motor..reasons for excessive fuel consumption
    1...fuel pressure
    2...leaking fuel system
    3... unserviced injectors
    4...faulty thermostat....YES you read right :) and also faulty coolant temperature sensor
    5...faulty MAT sensor operation
    6...faulty MAP sensor operation
    7...and another one you won't believe...BUT IS true, faulty engine cooling fan operation

    others include as standard procedure....spark plug servicability and air cleaner
     
  8. BR377

    BR377 Guest

    I have been waiting forever for someone to post what you just did, Now i can check all these things :) I had no idea really what could cause over usage of fuel, after a few days the back of my car is covered in black speckles lol.
    I have a new thermostat, plugs, air filter & cooling fan wiring :) so its something else.

    So what does the 02 sensor do then???
     
  9. BR377

    BR377 Guest

    Oh and BTW, what are these?
     
  10. samuels

    samuels Active Member

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    senses oxygen in the exhaust gases......technical gaga for emission controls :)
     
  11. samuels

    samuels Active Member

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    sorry ....forgot to answer these 2 :)
    MAT......manifold air temperature
    MAP......manifold absolute pressure
    a brief explanation,as your control unit recieves information from various sensors it adjusts the timing,the amount of fuel,also recieves signals of barometric pressure.....air pressure,coolant temperature,etc,etc,etc,which plays into everything as well.....timing and fuel amounts
     
  12. BR377

    BR377 Guest

    Thanks for that Samuels, i will have to go 'have a play' and see whats going on!
     
  13. Cheap6

    Cheap6 New Member

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    The O2 sensor has final say over the fuel/air ratio so, yes it can affect fuel economy.

    With black speckles over the back of the car I would add a worn motor. The black speckles being oil in that case.
     
  14. Michelson4301

    Michelson4301 New Member

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    an O2 sensor effectively compares the amount of oxygen left in the exhaust gases compared to the amount of oxygen in the atmosphere so if the body of the sensor is covered in dirt and/or grease then it will read incorrectly. The O2 sensor effects BL- Block learn or fuel trims (there is both long term and short term fuel trims) Earlier model vehicles i.e. VN,P,R V6 and VN-VT 5.0l use BL where as VS V6-onwards and VT 5.0 MAF sensored systems (the difference between the 5.0ltrs are the way in which the computer senses load i.e. MAF(MASS AIR FLOW) or MAP )) and systems that follow use long term and short term fuel trims which are a % of original map. BL is usually set at factory to 128 there are 15 load points which all read 128. Load 15 is full throttle. As an example if your vehicle has an exhaust leak or a slow reacting O2 sensor then the computer will see excess air and dependant on load will increase the BL until Stoichiometric ratio is met(14.7:1). This is where your excess fuel consumption comes into it. The computer can increase the BL up to about 150 units before it sets the code for O2 sensor always reading lean then goes into limp home mode, this will be up to 20% more fuel. On the other end of the scale it can go as low as 97 i believe before it sets the code corresponding to O2 sensor always reading rich and go into limp mode. So you could have an increase of 18% more fuel being injected and and still not set your engine light
     
  15. BR377

    BR377 Guest

    Thats what i initially thought but its fuel, if i start the car and rev the thing when its cold i can smell fuel real bad, she is running richer than bill gates.
    It smells like fuel and it sure as hell goes WOOSH when you light up the puddle it spits onto the concrete if you redline it at startup hehehe.

    I am not 100% still but there is no oil burning smell and after 10,000km its still the same level, hasn't burnt any!
     

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