From what i've read on the dc2 forum, an O2 sensor doesn't have to throw a CEL to be fecked. Im about to test this as my Coupe has dreadful mileage(even compared to the S!)/emission issues and isn't throwing a CEL so i bought an O2 sensor of ebay too.

 

Could a failed or failing sensor cause the car to over fuel?

Reason I ask, is mine has a little habit at the moment of throwing up CEL lights when cold, and when it is not run for a day or two.
When the CEL is on and you try to cold start it, it somethings takes a good few turn overs before it fires up, but then it'll cough and splat abit.

When the car is upto full temp, it runs like a dream, and when it is hot it'll again re start without issues.

So far I have brought and fitted:-
New Map Sensor
New ECT
New Thermostat

And the problem is still there.

Cheers
Kiwi

 

Sure!
The ECU gets wrong signals, i.e. data that does not reflect the actual values.
Hence it either under- or over-fuels

 

As the car gets older the sensor obviously gets older and more used. I however dont think there is a problem with my car and its high mileage otherwise I'd of noticed the issues pointed out above.

It works by a voltage signal that goes up and down depending on oxygen levels, it could produce an unchanging signal or non at all!. I'd of imagined when this happens the CEL light may come but as pointed out above it hasnt , since you can monitor it i would have thought they would have put a threshold on for voltage so when its currently reading 0v etc its fuoked and therefore put a CEL light on.

The problem with a knackered one are pointed out by shepp, problems caused by an overly rich fuel condition cack mpg etc.

You can clean them in a sense (not 100%) buts it better to replace and at 14quid.

Another reason why my program for my mobile phone I'm developing is useful because i can read the voltage of the lamda sensor

Though I'm not sure what voltage is healthy but I'll look it up.

https://www.s2ki.com/forums/index.php?showtopic=678753

 

Hello Kiwi
Regarding your cold start problems, the sensor has a pre heat function, the two white wires, the sensor does not work untill it is up to approx 300 deg hence the,pre heat function, It could be an issue that yours is not pre heating, giving the ecu incorrect readings when cold,
Just a suggestion, worth a try at

 

Well I have brought the above suggested sensor, worth a try

Kiwi

 

Hello AJ
The only problem with checking the sensor is
firstly
the out put is variable depending on conditions
secondly
the are to test is very hot, plenty of burns and cursing while trying to get a reading
thirdly
any instrument that is heated and cooled to such an extent does loose a degree of calibation accuracy.
to test it properly you would require a test pipe, and heated monitored gas supply so you could check the variable output

 

Let us know how you get on?

 

But reading the values when you've had the car and warmed it up and thrased it, you should get values back in volts depending on differing scenarios.

Remember with my program on my mobile, I'm not physically removing the sensor I'm reading directly what the ECU reports from the OBD2 port by the passenger footwell.

Now If the sensor was feked the signal was give back an odd voltage, ie none changing signal or none at all ie 0volts.

What i'm getting at is your lamda sensor would of given these none changing voltage values or non at all, obviously it was fecked thats why you replaced it



Please correct me if im wrong, its seems logical to me.

 

when s is cold on start up it revs up auto choke when it starts to get warm the revs drop ten mins later ok is this same probs ?