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Discussion Starter · #1 ·
hi,

I have recentyl purchased an EVO 6, I took it into a Mitsu garage on monday for a quick check... As a bought it private.. After the hour chack over the guy said it needs a new Oxygen sensor, as its not showing up on the diagnostics chart or summit..

My question is, what does this sensore do? (obviouse Answear maybe, but i would like to know more) And what damage could happen to my car? I am getting it sorted ASAP, but just wondering..

Any help would be great, thanks!
 
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Discussion Starter · #2 ·
An oxygen sensor (hego, lambda etc) measures the amount of oxygen in the exhaust gasses the amount of oxygen will be dependent on weather the engine is running rich or lean it the sends an electrical signal(voltage) to the ecu and then ecu working with other engine management sensors with adjust the mixture acordingly. They have quite a narrow opperating band(mixture wise) and have to be up to temperture before working. Most sensors now have there own heating elements inside to help the mixture control from cold starts.

Hope this helps

Sean
 
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Discussion Starter · #3 ·
As Shaun say most have heaters as does the EVO VI which pretty instantaneously raises the temperature to 300C when you start the engine. You won't get any reading much below this.

I wouldn't have thought that a faulty sensor would cause damage as I think the ECU goes into a safe mode, and in any case when you've got you foot planted the fuelling will be determined by the ECU map rather than information from the sensor. Is is more likely to cause the engine to run roughly at tickover or when its warming up from a cold start or something.

Steve
 
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Discussion Starter · #4 ·
Personally I never believe anything a technician says without proof but that is just me ;)
The oxygen sensor is situated in the exhaust manifold (look down the left front side of the exhaust manifold heat shield) and as has been said above is there to determine the fuel/air ratio in the exhaust.
Follow the wiring back from the sensor and check to make sure it is not damaged or the connector is not loose, you can also do some other checks if you have a multimeter.
First you can quickly check whether the heater is working in the oxygen sensor.
Find the connector from the oxygen sensor and disconnect it. Measure the resistance across terminals 1 and 3 (thats blue/yellow and red wires). At 20oC there should be continuity (11 to 18ohms). If there is a high reading then the heater element is faulty and a new oxygen sensor is required. You can also check to make sure the actual sensor is operating correctly but that is slightly more involved as you have to measure the voltage while the oxygen sensor is connected up with the heater working. Bascially though the output voltage across the sensor should be 0.6 to 1.0V when the engine is raced repeatedly (thats terminals 2 and 4 or black and white wires).
I hope this helps.

btw the heated oxygen sensor appeared on the E5 onwards, the E4 oxygen sensor was unheated.
 
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Discussion Starter · #5 ·
I thought that would flag a check engine light - my VR4 had an intermittent oxygen sensor for about 4 months (CE light on and off randomnly - code 11?) - no adverse effect on drivability or fuel consumption - spark plugs remained proper colour. When it finally came out (boy did that require some torque on the socket!) When replaced there was no noticable difference in how the car ran at all. The default safe open loop maps are obviously pretty good. Not so sure if it's a wildly modified car - and it probably doesn't do the cat any good - not that many evo people seem to use these! I'm not recommending anyone to drive around with a duff sensor - if it truly is knackered then get a new one fitted. Check it as per HH6 (did that guy swallow the workshop manual at birth?!).

Do the evo's have an O2 sensor check connector in the loom near the wiring harness? - a digital multimeter on that (grounded to ecu ground) will also tell you whether it's working or not. I now have a 'blinky light' Autometer Air Fuel gauge (www.buschurracing.com) attached to mine as an extra sensor check - not too accurate for tuning I know - but better than nothing. There is a guy in US who modifies Autometer AF gauges to give them more accurate smaller voltage range as a tuning aid for all those DSM (www.dsm.org) drag boys over the pond. Other fave is Jumptronix LCD gauge (www.roadraceengineering.com)

BTW - US E39 VR4's had 4 wire - JDM spec 1 wire O2 sensor.
 
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Discussion Starter · #6 ·
Thanks

Nice one for the info on he sensor lads.. I will try and check this my self whn i get back from work.. But a new one is around £230 i think he said, if i do need a new one, its lucky my car is still under warranty init! (hope they folk out for this) http://www.lancerregister.com/graphics/tongue1.gif border|EQU| 0 align|EQU| absmiddle >

Thanks again..
 
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Discussion Starter · #7 ·
HH6......just as a general point of interest the sensor without the heater operating will heat up to 300C within half a mile or so of driving, and once upto that temperature it won't drop below this even for extended periods at tickover.

I only know this from my experience with the EvoLink ECU which does not operate the Lambda heater, and hence I get no reading (voltage) on the Lambda gauge until the EGT rises to 300C or more.

What sounds odd is that if a damaged sensor seems to have no impact on the performance of the car, does the Factory ECU work in permanent open loop mode in anycase? If that is the case then I wonder under what circumstances the ECU relies on information provided by the Lambda sensor.

Steve
 
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Discussion Starter · #8 ·
Steve
Most cars go into a default mode if the lambda sensor goes down, usually the car runs very rich on idle and gets progressivly leaner as the revs rise.
Djack if you do need a new one i should check around £230 seems alot of money after all there are only two main types of sensor- titania and zirconia and wether they are heated or not - no. of wires

Sean
 
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Discussion Starter · #9 ·
If you want to check up on price parts then go to http://www.coordsport.co.uk.
I was just looking for the Oxygen Sensor and guess what I saw?

MR477547 AYC ECU E5-E6 £297.28

Do you think they have them in stock? I think they only list the stuff they have in stock.
Anyway I couldn't see the Oxygen Sensor. £230 seems excessive (more like £90 I would have thought at the most) but then again all their prices are excessive!

I must admit their searching is crap but I have just tried something that never used to work! Try selecting the car model then search (don't select what part types you want). You should get a list of all the parts available (over 1400 for the E6 GSR) and it makes some very interesting reading!
GRPA brake discs and bells for a total of £1000
Drummond Shock set £3423.76
etc...etc....
Have a look if you have a spare five minutes ;)

Sorry to go off topic :(
 
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