TCT 2.0i [Xm] fluctuating CO = fail!

Deanxm · Post by **Deanxm** » 01 Feb 2011, 21:57

should be changed every 50k really as they are very important. Cats and genuine O2 sensors aredirt cheap now for these if you look in the right places.

D

andmcit · Post by **andmcit** » 01 Feb 2011, 22:09

The figures are depressing:

Natural Idle
________________Min Limit___Max Limit___Actual Limit___Pass / Fail
RPM______l/min_______700______1000____________821__________Pass
CO_______%/Vol_______n/a_____0.500___________0.461__________Pass

Fast Idle
________________Min Limit__Max Limit____Actual Limit___Pass / Fail
RPM______l/min_______1950______2550_________2315___________Pass
CO_______%/Vol_______n/a______0.300_________0.450___________Fail
HC_______%/Vol_______n/a_______200___________25___________Pass
Lambda______________0.970_____1.030_________1.034__________Fail

Second Fast Idle
________________Min Limit__Max Limit____Actual Limit___Pass / Fail
RPM______l/min_______1950______2550_________2084__________Pass
CO_______%/Vol_______n/a______0.300_________0.310__________Fail
HC_______%/Vol_______n/a_______200__________15____________Pass
Lambda______________0.970_____1.030_________1.022__________Pass

Nearly got the pass with the second idle test.
Anyone care to decipher these figures please?

Andrew

andmcit · Post by **andmcit** » 01 Feb 2011, 22:17

What does the lambda figure above actually mean - does this suggest that
it's OK? The new spare I got for the Xantia is miles too short in length for the
feed up to reservoir connection. Would be about 4 feet in length as opposed
to about 10"!!

Andrew

Deanxm · Post by **Deanxm** » 01 Feb 2011, 22:20

Any 4 wire sensor will do Andrew, just cut and join the wires wherever you want, idealy Lambda should be a 1.0 yours is a little high and she's running rich as a result giving the high CO2, second tst being better is normal as the engine is hot and combusting more efficiently.

D

andmcit · Post by **andmcit** » 01 Feb 2011, 22:27

Thanks Dean/David.

So you're saying I should swap the lambda sensor then? Will it even unscrew
off the cat!!!??? I had some spare cats with sensors but the scumbags took
them when my barn storage was fleeced out.

I checked the temperature sensors on the head and they seem well clicked
on and the wires are OK under the brittle sheathing. This was the problem
throwing out the Xantia 2.0 8v - the figures were off the chart and it was
damned thirsty - this Xm seems OK on fuel TBH.

Andrew

andmcit · Post by **andmcit** » 01 Feb 2011, 22:31

Drawn a blank with this Turbo Pressure Valve too! Red Herring?
That's what the EML is flashing up for.

Andrew

Deanxm · Post by **Deanxm** » 01 Feb 2011, 22:34

Mine is getting the same high CO2 readings as yours although my Lambda is at 1.0 CO2 is high and i think the cat is dead, thankfully my cit dealer understands the pain and put the car through on a non cat test (ssshhhhh

)

plus gas is your friend when it comes to removal of the old sensor, it may well kill the atmospheric sensing bit of it but its going in the bin anyway so it wont matter.

shame about the cats Andrew, probably went into funding my big fat gypsy wedding somewhere

D

andmcit · Post by **andmcit** » 01 Feb 2011, 23:15

One thought I have having done a bit of Googling. It may seem obvious
but didn't worry the tester but there's the sound of a rasp on the manifold
which obviously is upwind of the lambda. Can this be an infamous TCT stuffed
exhaust manifold gasket screwing up the emissions as the lambda is getting
all sorts of duff readings and adjusting the mixture? I must say, I don't fancy
tackling this and the MOT man didsn't voice any concern about this...

Andrew

Deanxm · Post by **Deanxm** » 01 Feb 2011, 23:23

Yes Andrew, any upsteam leak will allow oxygen to enter the exhaust and can play havoc with the exhaust gas readings, are you feeling brave?

D

andmcit · Post by **andmcit** » 01 Feb 2011, 23:26

So this nicety is a dead cert - it needs doing?

Is it really as sh!t a job as described for Activae? I still have the mental
scars from a replacement of a cracked exhaust manifold on a Xm 2.0i 8v.

Is the gasket only OEM Cit?

Andrew

Post by **RichardW** » 02 Feb 2011, 12:24

You've got high CO, but also high Lambda, which suggests oxygen still present. I would be leaning towards the cat being suspect. You can check to see if the cat is working by using an infra red thermometer on it and seeing if there is a significant difference inlet to outlet. If you've got an oscilliscope you can check the output of the Lambda sensor is fluctating appropriately.

citroenxm · Post by **citroenxm** » 02 Feb 2011, 12:42

Andrew,

A Lexia WILL connect to this car and WILL read the ECU goings on for you, in a live parameters!

It uses the larger plug which I have on my Lexia Kit. Ive used it on my S1 L reg Xantia TD... Ok, so I could only read the ABS ECU... but my mates XM 2.1 td I was able to read the Suspension ECU...

You could be dooing a could be this could be that all YEAR... youd need to hook up and see what the ECU is reading or not reading in the Live Parameters section...

I had a simmilar problem on a customers 1.4 Xsara... it would stall - a bitch to start then when she did smelt of rich fuel. Turned out the ECU was not getting a reading from the GREEN water sensor... swapped it for another and it didn;t stall again.. so far! And seemed better on fuel

Paul

andmcit · Post by **andmcit** » 02 Feb 2011, 19:24

Problem is I'm somewhere close to nowhere when it comes to getting
it Lexia'd or having a cat scan!

I'm quite compellingly convinced by extensive Googling that the rasp and
'flutter' that is quite noticeable from the exhaust manifold can be doing
readings to the cat's lambda no good at all - it apparently needs to be
critically pressurised and if there's an air leak all the fuel injection ECU
does is lose the plot. TBH, it's something I've been aware of and have
dreaded doing but I WILL have to bite the bullet and attempt a new
Exh manifold gasket. Duly ordered one for 32quid due in Friday. Guess
what I'll be doing this weekend...

From there I do not know. I believe changing the lambda is just changing
a messenger, not dealing with the main root problem/opponent though it's
true that a continued incorrectly set up engine can ruin the cat over time
but take heart that the figures don't signify blatant problems.

Is this the correct plan of attack? Still need to work out what this Turbo
Pressure Valve is according to Mr Gunsons and the charcoal jobby Dean
mentions.

Andrew

Post by **xantia_v6** » 02 Feb 2011, 20:01

If the cat is tired, it will work better when it is hot. My Xantia V6 will only pass the MOT emissions now if the tester revs it to 3000 RPM for a minute before doing the fast idle test at 2500 (which it then passes easily). Fortunately I have an understanding tester, but I must look out for another cat.

So if the emissions get better with a hot cat, I think it is almost certainly your cat at fault. BTW, I think your lambda results indicate that your lamda sensor is OK, and your exhaust leak (if any) is not significantly affecting the result.

robert_e_smart · Post by **robert_e_smart** » 02 Feb 2011, 20:15

Andrew,

The white TCT manual that I had, passed its MOT with a minced exhaust manifold gasket. It didn't affect the emissions testing.

I'd be inclined to get it MOTd before going to the hassle of changing the exhaust manifold gasket to find that its not the problem. The exhaust gasses will be leaking out through the manifold, and not actually drawing in any fresh air surely??