BX Tech talk
tim leech


Post by tim leech »

I know its not a BX but I really need to pull my finger out with the Xantia as its been sat Idle for 6 months. The cars ok except that the emmisions are too high, and it wont pass its MOT ive changed the lambda probe and that didnt make any difference, alos the engine check light comes on after a few seconds but the car runs perfectly

It does use some water but thats sue to aeaping radiator, theres no oil in the water etc.

Is there anyone localish that I can pay to fix this, if its a cat thats gone I nee dto know before I shell out £100 for a new one! Ta!

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Post by AndersDK »

dear Tim -

A bad/missing cat will not influence the engine management system :roll:
- only the MOT test
Thats because the Lambda sensor is sensing the gas BEFORE it enters the cat :D
As it failed its MOT on emissions - and you get the engine management fault light on - I honestly doubt its the cat at fault. Must be something around the engine management system at fault then.

My 2 favorites are the MAP sensor and the CTS sensor. But the ATS may play up as well.
All can be tested by disconnecting them (one at a time please !). If nothing happens/changes - then you may assume that the disrupted sensor dont do its job when connected. Either by itself or by a faulty cabling.

You can still use the engine fault lamp as indicator for a behaving engine management system. Once you have the fault lamp to stay out - you have come over the problem.
But the fault code will still stay in memory for quite a while.

Have you got out the fault codes ? They are usable as hints towards the problem - but rarely pinpoints a sensor.
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Post by tim leech »

Anders thanks for the advice but Im not technically mided so its all gibberish to me! I changedthe lambda but do you think the new one could be faulty?

The car itself is a just a 1.8i 8v engine so not too complicated. Single point injection I would expect too as its only 103bhp

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Post by cavmad »

Have you tried an oil and filer change, some fresh fuel and then giving it the pasting of a lifetime up/down your nearest motorway or bypass?
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Post by sleepy0905 »

That worked for my emmisions on the tzs which failed at 3.9 did the above and it came down to 3.4
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Post by Ian_Fearn »

Anders, can you explain your 3 letter acronyms?

I'll probably end up helping Tim with this.
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Post by Kitch »

I would have also changed the lambda. But if the lambda has been faulty and the car has been overfueling, this may have broken the cat down a bit causing the emissions to read high. To be honest though, a car SHOULD still pass an MOT with no cat, whatever the year. Cats are just there for the green open toed sandle brigade.

However short of changing the air filter and plugs (ignore fuel filter as the more blocked it is, the leaner the car will run!), I'd get the car hooked into a diagnostic computer. Its about £40 and it tells you whats what.

Could even try some fuel additive, but most of them are bulls**t and petrol has plenty of cleaning agents in already.
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Post by jeremy »

Its possible that there is actually nothing wrong with it - and that the emissions are due to a build up of unburnt fuel etc in the exhaust - simply due to the car being stopped and started many times and never having got hot. In an extreme case you may need a new back silencer to shift the problem.

I used to work with a guy who drove his car a very short distance to work every day and never really went anywhere else. His car failed on emissions and the cure was a new back silencer!

So a good blast as suggested by Cavmad may be the answer.