Xantia - Bad smell from the exhaust system

addo · Unread post by **addo** » 28 Jul 2011, 14:43

That does not sound particularly excellent! Only one oxygen sensor in these cars.

If you do change it, my method is to disconnect the centre exhaust section and allow the catalytic converter to hang lower. This improves access a lot.

lancia58 · Unread post by **lancia58** » 29 Jul 2011, 05:54

Hi

Should I go for a genuine Oxygen sensor or an aftermarket is as good

Thanks
Zohar

addo · Unread post by **addo** » 29 Jul 2011, 09:37

I personally would be happy with the "good" brands - either Bosch or NTK. Not sure about the lifetime of parts like that, made in Asia.

MikeT · Unread post by **MikeT** » 29 Jul 2011, 10:06

lancia58 wrote:Hi

I checked the Oxygen sensor using the Lexia, the voltage jumps form 150 to 800 but it was very erratic. For example I recorded the following consecutive readings 776, 561, 439, 732, 195, 664, 156, 644, 146.The engine was at idle. Is that a normal behavior or it indicates a faulty Oxygen sensor ? Is there one Oxygen sensor or more ? The car engine is 2.0 16v

Thanks
Zohar

Those readings look typical to me.

Take a read of this and judge for yourself. http://mr2.com/TEXT/O2_Sensor.html

lancia58 · Unread post by **lancia58** » 31 Jul 2011, 17:52

Hi

Can the fuel consumption be OK even if the Oxygen sensor is faulty ?

Thanks
Zohar

Unread post by **CitroJim** » 31 Jul 2011, 18:38

lancia58 wrote: Can the fuel consumption be OK even if the Oxygen sensor is faulty ?

Often not. High fuel consumption is a bit of a give-away.

before condemning the lambda sensor, take it to a friendly MOT place and ask them to stick a probe up it's tailpipe to see if it'll pass an MOT on emissions. If it will then the lambda is likely OK...

lancia58 · Unread post by **lancia58** » 31 Jul 2011, 18:56

Hi

It passed the MOT test on January and it was on the edge , the guy told me that I’ll better change it because it is on the edge. The thing is that the fuel consumption at freeway driving is excellent. This is why I ‘am confused . I test with the Lexia you can see the test result in a previous post of this topic

Thanks
Zohar

Unread post by **CitroJim** » 31 Jul 2011, 19:08

In what way was it on the edge in January Zohar? Was that the lambda reading? HC reading or CO reading?

If the lambda was on the edge then the sensor is due for a change. High CO indicates a dead cat and high HC indicates a rich mixture or misfiring.

The Lexia lambda reading will be hard to interpret as the lambda output voltage is constantly changing. Best to look at it on an oscilloscope and it should them look like a slow sine wave. Under normal conditions with a good lambda the voltage should slowly vary between about 150 and 800mV and as said, describing a sine wave shape. A very fast change of lambda voltage tends to indicate the sensor might be past its best.

because of the changing nature of the signal, the lexia is not the best method to measure it unless you have a pukka Lexia 2 and can use its built-in oscilloscope; this will give a much better picture.

lancia58 · Unread post by **lancia58** » 31 Jul 2011, 19:55

Hi

What is the expected frequency of the sine wave ? The Lexia updates the reading approximately each 0.5 second. The readings were erratic, and defiantly changed fast .. I’ll try to record more tomorrow and using an Excel sheet to see if it describes a sine wave.

Thanks
Zohar

Unread post by **CitroJim** » 31 Jul 2011, 22:09

Not sure of the exact frequency Zohar but it should be slow, say between five and ten seconds for a complete cycle I'd guess...

addo · Unread post by **addo** » 31 Jul 2011, 22:32

It's faster than that; the cycle repeats every two and a half or three seconds... A good Xantia O2 sensor should top out almost 100 mV higher than those readings.

lancia58 · Unread post by **lancia58** » 01 Aug 2011, 06:01

Hi

I found this link it sais the frequency is 1 Hz, the Lexia sample rate is too low to see if it changes at a rate if 1Hz, the only possibility is sign an oscilloscope

http://www.autodiagnosticsandpublishing ... esting.htm

http://www.aa1car.com/library/o2sensor.htm

Thanks
Zohar

lancia58 · Unread post by **lancia58** » 09 Feb 2012, 07:20

The Lambda is 1.01 and the CO is 0.09 for 780 RPM and 0.12 for 2600 RPM . Do these measures indicate on a faulty Oxygen sensor ?

Thanks
Zohar

DickieG · Unread post by **DickieG** » 09 Feb 2012, 08:04

lancia58 wrote:I found this link it sais the frequency is 1 Hz, the Lexia sample rate is too low to see if it changes at a rate if 1Hz, the only possibility is sign an oscilloscope

Lexia has an oscilloscope built in which you can access via the diagnostics menu.

VertVega · Unread post by **VertVega** » 09 Feb 2012, 19:09

Just noticed that the thread was started July 2011 and I guess the cause of the bad smell was also found?

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Xantia - Bad smell from the exhaust system

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