BX XU PETROL BOTTOM PULLEY

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Tim Leech
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Post by Tim Leech »

mat_fenwick wrote:Do you know whether you can read out live data from the lambda sensor via the OBD socket? Failing that a fast acting voltmeter or an oscilloscope might be needed to see whether it is switching correctly.
Erm????
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BX Meteor
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Post by BX Meteor »

I took this from the web (I used to know this, I briefly worked in an engine test lab at Rover in 1991) ....
"Lambda sensors produce a voltage signal that recognises the amount of unburnt oxygen in the exhaust. An oxygen sensor is essentially a battery that generates its own voltage. When hot (at least 250 °C), the zirconium dioxide element in the sensor’s tip produces a voltage that varies according to the amount of oxygen in the exhaust compared to the ambient oxygen level in the outside air. The greater the difference, the higher the sensor’s output voltage.

Sensor output ranges from 0.2 volts (lean) to 0.8 volts (rich). A perfectly balanced or "stoichiometric" fuel mixture of 14.7 parts of air to 1 part of fuel gives an average reading of around 0.45 volts.

The lambda sensor’s output voltage doesn't remain constant, however. It flip-flops back and forth from rich to lean. Every time the voltage reverses itself and goes from high to low or vice versa, it’s called a “cross count”. A good O2 sensor on a injection system should fluctuate from rich to lean about 1 per second. If the number of cross counts is lower than this, it tells you the O2 sensor is getting sluggish and needs to be replaced.

Most lambda sensors will cycle from rich to lean in about 50 to 100 milliseconds, and from lean to rich in 75 to 150 milliseconds. This is referred to as the “transition time”. If the O2 sensor is taking significantly longer to reverse readings, this too is an indication that it is getting sluggish and may need to be replaced."

Basically, the exhaust gas is not a smooth flow, there are all sorts of fast pumping eddies going on in the exhaust.

Also, remember the first rule of trouble-shooting ..... never assume that a brand new part is not faulty.

As Mat says, get an oscillosope (I used to have one but not any more) and you will see the waveform, or maybe try a DVM as Mat says.

Doubtful if the pulley will get you anywhere, if your cam timing is out, there are plenty of other ways to find out (in the opinion of most people who have posted it seems), and if you had the problem before the cambelt broke, then cam timing is a low possibility.

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Post by mat_fenwick »

I doubt a DVM will react fast enough to signal the lambda switching, but an old analogue meter should. But you may be able to read out the lambda voltage via the diagnostic socket. I would have thought a reasonably clued up garage would have checked this one way or another.

Does/did it improve when you floor the throttle? The ECU will go 'open loop' above a certain rpm or throttle opening and hence ignore any reading from the lambda sensor. If it is still the same at full throttle that would tend to rule out the sensor as the sole problem.
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Post by Tim Leech »

When you cane it the emissions do drop slightly but nowhere near enough to get through an MOT.
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Post by mat_fenwick »

I meant do the lumpiness and sluggishness clear up at full throttle?
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Post by docchevron »

mat_fenwick wrote:I doubt a DVM will react fast enough to signal the lambda switching, but an old analogue meter should. But you may be able to read out the lambda voltage via the diagnostic socket. I would have thought a reasonably clued up garage would have checked this one way or another.
We've certainly got real time info from plenty of later Xantia's at the garage. I see no reason why it shouldn't on this one.

AFAIK the bottom pulley from a 16 or 19 8V BX engine is not the same as a Xantia pulley, BUt new shiny pulley's are available from the stealer, so that may be your best bet, unless someone on the CC or FCF can sort you out a used one?

Personally I'd use a dial guage (or the methods prescribed on here) to set the engine to TDC then refit the belt.
If at that point it runs as it did you are at least back to square one, from there I'd be checking the lambda tolerances and run it with the air mass unplugged, if it makes a noticable difference then we're getting somewhere.
Smokes lots, because enough's enough already!

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Post by Gary »

I take it that it is a 1.8 8valve if so they have always been a problem when it comes to mot emissions, our local mot tester used to disconnect the the fuel pressure regulator and load the engine using the heated rear window and turning on the head lamps.
I think the figures supplied to vosa by the manufacture were optimistic

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Tim Leech
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Post by Tim Leech »

Hi Gary

Yes it is a 1.8 8v.

Worth a try I expect!
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Post by bx petrol auto saloon »

Dear Tim.
Hows the car coming on then Tim, any joy yet :wink:
Vince.
Passion Hydropneumatic Citroen,s

Cars;- 1993 White Citroen BX 1.6 TXi petrol
saloon auto with air-con & ABS.
47,594 Miles from new.
Owned for 3 years sorned.
1988 Silver SAAB 900i 2.0 8v F/lift,
saloon 5sp with 3 spoke Ronals,
69,000 Miles from new.
Owned for 15 years T & T.

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Post by Tim Leech »

Nope its still fucked. After having the timing reset, the cambelt and waterpump changed and £200 lighter its no better. Its going down to Dickie G from the FCF who is a Xantia expert, inbetween xmas and new year and he is making it his challenge to get it running right!

Failing that its going to sit and rot.
Lots of Motors, mostly semi broken....

bx petrol auto saloon
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Post by bx petrol auto saloon »

Dear Tim.
I am so sorry to hear that Tim :( They are lovely looking cars
Xantia,s, When I was looking for the BX, I saw a lovely automatic one
for sale with 15,000 miles from new and one owner etc.etc. but the only
problem with it was the fact it was silver, which is not my favourite
colour for one, but it was very nice though 8)
I know how you feel though, I am exactly the same myself, I always
think that you can get to the bottom of any problem, with patience and
logical processes and downright stubbourness not to give in until it is
sorted one way or another :!:
I hope Dickie manages to sort it, what I used to do in bad cases like
that, I use to start with a new car out of the showroom, and start
swapping bits until it was cured. the sales manager never did like me
doing that though :roll: it is the only route to use on yer xant, Tim.
available to you.
All The Best Tim.
If you ever need anything just shout OK :?:
Vince.
Passion Hydropneumatic Citroen,s

Cars;- 1993 White Citroen BX 1.6 TXi petrol
saloon auto with air-con & ABS.
47,594 Miles from new.
Owned for 3 years sorned.
1988 Silver SAAB 900i 2.0 8v F/lift,
saloon 5sp with 3 spoke Ronals,
69,000 Miles from new.
Owned for 15 years T & T.

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BX Meteor
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Post by BX Meteor »

it probably needs an exorcism

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Tim Leech
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Post by Tim Leech »

If I thought It would do the trick I would happily try it!
Lots of Motors, mostly semi broken....

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Tim Leech
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Post by Tim Leech »

She is now in the very safe hands of Dickie G and Sir Jim, I waved her off at 4pm today as we headed home as the trailer needed to be back by 6pm. A phone call at 10pm and they are still at it and making progress, those guys your Xantia legends! :-D

The towcar was a rather unlikely candidate....a fabulous towcar but got through £70 worth of diesel going there and back today :oops:

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Lots of Motors, mostly semi broken....

bx petrol auto saloon
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BX XU PETROL BOTTOM PULLEY

Post by bx petrol auto saloon »

Dear Tim.
That is a nice towcar Tim, what is it though :?:
It is very very nice of Dickie and Sir Jim to have at the Xantia for you
Tim. I hope everything goes OK with her Tim :wink: and that you can
soon look back on this and still smile :)
All the best Tim.
Vince.
Passion Hydropneumatic Citroen,s

Cars;- 1993 White Citroen BX 1.6 TXi petrol
saloon auto with air-con & ABS.
47,594 Miles from new.
Owned for 3 years sorned.
1988 Silver SAAB 900i 2.0 8v F/lift,
saloon 5sp with 3 spoke Ronals,
69,000 Miles from new.
Owned for 15 years T & T.