TCT 2.0i [Xm] fluctuating CO = fail!

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andmcit
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TCT 2.0i [Xm] fluctuating CO = fail!

Post by andmcit »

This particular Xm has been borderline pass/fail the past few years but
wouldn't play ball this morning and failed it's CO2 readings on the
emissions. The mileage is 100k miles and it's been looked after and
serviced. The HC readings are negligible. During the high speed revs
test figures ranged from 0.26 to 0.70 with the pass threshold of 0.30.

It would hold at 0.26 for just short of the magic 10 seconds but seems
happier at 0.46. It's just had new plugs, oil and air filter and an 'Italian
tuneup' but it's not getting any better [worse in fact]. The tester idled
the car and revved using the manifold throttle spindle and said he could
feel the pulsing of the engine as if the injectors were uneven and could
see the effects simultaneously on the emissions meter readings.

Where do I start? I'll certainly look at the temperature sender as per a
Xantia a month ago where the multi-plug wasn't connected properly and
it was throwing the whole engine management. I've had occasional cutting
out and trying to restart turning over seems to leave a rich petrol smell
as if it's flooding or there's no spark; I've tried a different ignition map
sender and even another ECU thinking it's an ignition issue.

The feed wires off the temp sensor look baked and the insulation is
cracking off but the wires don't look like they're shorting out but
that area of the engine does get VERY hot!!

Do I try a set of injectors off another Xm I have running?

Ideas and points to check would be very welcome although my car
electrics understanding is basic although I have a more qualified
multi-meter!!

Andrew
Last edited by andmcit on 08 Feb 2011, 21:13, edited 2 times in total.
andmcit
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Location: Swansea - South Wales
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Post by andmcit »

Oops, mileage is 100k. Engine management light sometimes
comes on and does good impression of ABS light! Car OK on
fuel mpg and seems happy to start.

'93 model so no Lexia?

Andrew
Deanxm
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Post by Deanxm »

Smells like Lambda sensor issues :lol: , when was it last changed Andrew? gunsons do a code reader that will tell you what the old girl is thinking, about £12 if i remember correctly.

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
Deanxm
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Post by Deanxm »

sorry Andrew, just seen its CO2! with the warning light it could be a duff map, tps or air mass sensor, may even be a knock sensor but im not sure on that, high co2 is because of running rich but it wont be the injectors with that management light, the ecu is being misled by one of the above sensors.

You can get the info from the carr via the green two pin plug in the ecu box but you need the two prong lead for the lexia.

Of course make sure its at a good temp, air filter is clean and plugs gapped right, also make sure the purge valve on the carbon canister is strutting its stuff as it should.

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
andmcit
Posts: 4299
Joined: 03 Mar 2005, 17:59
Location: Swansea - South Wales
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x 30

Post by andmcit »

Hi Dean, thanks for the input; I posted here as most Xm guys only DERV
anyway!

The car seems to intermittently flash the EML - it's not permanent. One
thing I do recall was swapping over a dead alternator: after that the
car has never felt the same and it's been around then the EML has been
on/off - guess there's chances of a leak or wiring damage on the OSF
corner? I seem to time the bad emissions scrape through MOT'd BEFORE
this though.

I have never changed the lambda but probably have a compatible one that I
didn't use on the Xantia though will need to check. I've tried an ignition
module swap on the side of the battery tray - in my naivety I believed this
is the MAP sensor!? Correct me if I'm wrong as it may help me have a
refresher in knowledge of these!!!! I'm happier with the CX's and GS's!

MrMOTman suggested a duff lambda could fool the ECU and lead it on
a merry dance where it could over fuel.

I'll see if my father has his gunson code reader to read off the loose plugs
in the ECU box - ATM the light isn't on if that helps...

Andrew
andmcit
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Post by andmcit »

Ok, and how do I check the carbon purge valve!!?

Andrew
andmcit
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Post by andmcit »

My dilemma too is the car is now illegal on the road with no tax or MOT
and no friendly home to seek refuge in - time for desperate measures
if I can't sort something out! :?

Andrew
Deanxm
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Post by Deanxm »

unplug the purge valve and it should fail open simulating a vac leak, plugging it back in will make the also be noticable to idle speed/smoothness, if there is no difference its bust but i would check the others first.

You can still drive the car back from the test station on a fail with no tax, so long as its not held by the mot station as dangerouse to drive, ie it has no brakes or has rusted in two.
I do it all the time, with sorn cars too!

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
andmcit
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Post by andmcit »

I haven't checked the purge valve as I've just got hold of the Gunsons PSA
code reader. I've rattled just one code: "46" out of the green fault code
connection as directed and it then sends an end of test trigger - so just one
code registered; according to the Gunsons chart this is a Turbo Pressure Valve.

Before I plough into my documentation now to decipher what this actually
means, anyone want to chime in with a cut to the chase interpretation for
me!?? :D

Andrew
Deanxm
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Post by Deanxm »

, well for my money its either solonoid boost controller......which wont really affect your mixture.
Or its the Map sensor which could cause your trouble, let me double check on my sheet.......

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
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Post by xantia_v6 »

Are you sure the failure is for CO2? I don't think it is part of the MOT test, only HCs and CO.
andmcit
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Post by andmcit »

Of course you're right - it's CO - the HC's are in single figures which I'm
told is excellent - about the only thing about these readings that is really.

:oops:
Deanxm
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Post by Deanxm »

thats a good point actualy, good job someones awake! must be CO. did it fail the natural or fast idle test Andrew?

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
Deanxm
Posts: 3327
Joined: 18 Dec 2008, 17:57
Location: Isle of wight
My Cars: Citroen XM
x 87

Post by Deanxm »

If HC is low then the engine is good, but with high CO you are looking at a Lambda sensor or Cat with a well kept car of this age with no leaky exhaust or inlet tract.

D
XM Prestige PRV6 92
Talbot Express Autotrail Chinook 89
Mitsubishi L200 Trojan 14
Xantia Activa 95, sold (missed)

Service Citroen is awesome, it shows me pictures of all the parts i used to be able to buy............
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Post by DHallworth »

We're going through exactly the same thing with one of the Range Rovers.

This one is a 4.6 and it runs rough and smells awfully rich when it's running.

Turns out on this one it was a pair of faulty lambda sensors as it would run ok for the first 10 - 15 seconds then when the lambda sensors got warm it was missing and running badly as the sensors were giving duff readings.

In turn the car was throwing to much petrol into the cylinders and not getting enough air. If you unplug the vacuum pipe on the inlet the car could get enough air and it would just about run.

If you've got one that'll fit it, that'd be my first port of call.

David.
'98 Xantia Activa V6 :-D
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