TCT 2.0i [Xm] fluctuating CO = fail!

[Deanxm]

Andrew

The charcoal canister sits in the wing of the car, the vent pipe from the fuel tank runs into the canister, then there is another pipe that runs from the canister via a solonoid valve to the inlet manifold and under certain circumstances as pressure builds in the tank the valve opens and vents the fuel vapour into the inlet tract where it is drawn into the engine and burnt.

Its just a method of storing fuel vapour and then burning it rather than letting millions of gallons of petrol evapourate into the atmospher each year.

D

[andmcit]

But that's the trick Robert, whilst I see what you're saying I need to get the
damned thing to pass it's MOT - the retest clock is now ticking. I fear I may
have to scrap it - I JUST HAVE NOWHERE TO KEEP ANOTHER UNTAXED CAR.

Andrew

[Deanxm]

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??

They will blow out when the leaking branch is exhausting and leak in while the others exhaust BUT (and i thought i had reply'd already) i would be checking this last, if it was a 10 minute job i would knock it on the head but with a TCT leave well alone for now, obviously it needs doing but i dont think its the root of your problem.

Also the pressure valve will be a red herring, it may well be faulty, but its not giving you the high CO reading.

Seems like the cat is prime suspect if it needs to be hotter to give better readings, obviously having trouble fully lighting the cat and getting a full reaction out of it.


D

[robert_e_smart]

http://www.cats-direct-shop.co.uk/catal ... ID=BM90243

This is what you need Andrew.

Scrapping your old cat will recover a good chunk of this cost. The last cats I scrapped were £35 each, but scrap prices have gone up a lot since, so I don't know what the current price is.

[steelcityuk]

I think that it's probably a leak that's causing the problems, the Lambda could well be old and slow too. Unless you use a genuine sensor you could have the EMU light up because the sensor readings could be different to what the EMU expects. I don't think the catalyst and lambda sensor is totally dead because the reading would be constantly high for CO.

Steve.

[andmcit]

I don't think the catalyst and lambda sensor is totally dead because the reading would be constantly high for CO.

That's what I've been reading Steve.

One site http://www.picoauto.com/applications/lambda-sensor.html does say:

If the lambda sensor continually reads low (lean), it will cause the engine
computer to enrich the fuel mixture. Injector pulse width will increase
causing fuel consumption and carbon monoxide emissions to go up.
Constant rich fuel mixture can also cause the catalytic converter to
overheat and it may be damaged.

Sometimes an apparent lambda sensor problem is not really a faulty
sensor. An air leak in the intake or exhaust manifold or even a fouled
spark plug, for example, will cause the lambda sensor to give a false
lean indication. The sensor reacts only to the presence or absence of
oxygen in the exhaust. It has no way of knowing where the extra
oxygen came from. So keep that in mind when diagnosing oxygen
sensor problems.

I realise the car when driven seems OK on fuel consumption but the fail
reading I'm getting are just tipped into the fail range of measurement.

I am considering fitting an alternate cat/lambda borrowed off another TCT
I have just to rule them out feel there's a throatiness rasp emanating from
the manifold that really shouldn't be there yet hasn't caused any MOT
comments - it's certainly not like a leak I am suffering with on an Activa
that sounds like a hole in the exhaust.

Andrew

[andmcit]

http://www.cats-direct-shop.co.uk/catal ... ID=BM90243

This is what you need Andrew.

Scrapping your old cat will recover a good chunk of this cost. The last
cats I scrapped were £35 each, but scrap prices have gone up a lot
since, so I don't know what the current price is.

Mind Robert, that's a good price but it's off a Xantia.
The Xm one all in will tip £100. A new lambda another £30-60.
I just don't like playing hunches with my wallet.

I realise a "part ex" weighing in the old cat may claw some cash back
but it's hassles and the guys around here that take the scrap are probably
the ones that took my x2 cars and car transporter trailer so you can imagine
I'm not in a hurry to speak to them.

Andrew

[andmcit]

I spent this afternoon attempting to examine the set up of the manifold on
a spare TCT engine and the cat/sensor on another XM. I must say even with
the engine on the floor access is a real PITA to the manifold shield and the
inlet/exhaust feed pipes. What a git.

It's actually been a while since the Xm has been given an oil change and
there's more past the dipstick max (10mm!! ) than I like so this
is a suspect and needs sorting tomorrow too.

This could even be the problem!

If not I'll try and rule anything/everything else out first but have some
blind spots here as far as the system goes. The symptoms point to overfuelling
with the engine running rich so the main points to check and rule out are:

• • temperature sensor (which one as there's a green, blue or purple one feeding different systems?)
  • Breaking down distributor/coilpack or HT leads running but not giving the full spark
  • manifold absolute pressure (MAP) sensor (is this the small canister on the bulkhead above the manifold feeds?)
  • airleaks in the miles of plumbing?

Yes, there is always a failed cat or lambda but apparently these don't make
a habit of failing and usually cop a problem from another failure upwind
and their replacements go the same way given more time!!

Andrew

[Deanxm]

In the case of the cat yes they should theoreticaly, last forever, but that is never the case and we are dealing with a car that has gone well beyond its expected life. Lambda sensors are considered service items and should be replaced at set mileage's, they are after all a key component controlling mixture.

What is the canister on the bulkhead, all i can think of around there is the boost controller, the Map sensor is built into the ECU and is not a simple replacement.

D

[andmcit]

Looks like a vacuum switch where all the rubber feeds seem to meet - it's
mounted onto the scuttle just a way along from the stamped chassis number.

I've read the oxygen sensors get lazy so yes, it could be but reading through
google the figures I've got don't directly point to a failed sensor. I take Robert's
point about a slightly fruity exhaust passing emissions as I recall I've done this
myself before so although there's "something" there on idle it's not like a holed
exhaust.

The plan for tomorrow is a replacement temperature sensor, and an oil change
with filter and the correct amount of oil! I've run the car over the past few
days on Redex injector cleaner and 97 Unleaded and it seems to be smoother
but may just be a placebo effect!

Andrew

[Deanxm]

Ah, on rubber mounts? that will be the ecu controlled boost controller, what i think your gunsons reader is telling you is faulty.

D

[andmcit]

So. Worth swapping another s/h spare with?

Andrew

[Deanxm]

yeah i would say so, im sure it has nothing to do with emmissions control or mixture but it will get rid of that damn orange light if its the cause.
Thats the trouble with the aftermarket code reader, they can be a touch vague.

D

[andmcit]

Me again and in a worsening situation I don't want to go into here...

Finally nailed down the meaning of the fault code "46" cross-referenced
with factory manual supplement. Pilot Electrovalve control which signifies
a major fault with the light on. Turbo pilot Electrovalve (wiring item 444)
feeds a signal direct to the ECU - it's a brown 2 terminals connector.
Like I say, apparently a serious fault so I can't ignore this. Just may be a
rogue sensor that's causing all my woes.

An "aid to repair" is code 88 although this sounds like a job for Citroen
magic box of tricks 4097-T or 4120 T etc. Figures show it should have a
resistance of 30 ohms?

First question! Does anyone know where the £@€¥ this item 444 physically
is amongst the metres of plumbing and wiring!???

Help! Any Activa savvy guys care to help!?

Andrew

[andmcit]

Another thing that's highlighted with the TCT supplement is a reference to
"Auto adaptation of mixture adjustment" on lambda probe; it does suggest
"-check the HT leads, the exhaust system for leaks (forward of the probe)".

Suggests a bit of fluffing at the exhaust manifold can screw about with the
ECU mixture. What a horrible job to do changing the gasket though!

I'm genuinely on the brink of weighing it in - I'm literally not managing
to cope here: would anyone be interested in this for the scrap value?
Must be 200quid with alloys and potentially dead (or maybe not) cat?



Andrew