Xantia XUD turbo lack of boost - lolingram
I have recently acquired a Xantia 1997/Rreg XUD Turbo estate in good general condition - 75KMiles. Shortly afterwards a lack of urge at the top end of the rev range has become apparent...

Another oddity is that when the engine is freshly started from cold, the boost is just fine; after it warms up the top end boost is lack-lustre, but the turbo can be heard whizzing away nevertheless - seems like not enough diesel being injected at the mid to top of the rev range when hot. Filters and the usual stuff check out OK.

Engine is 1.9 XUD with mechanical Bosch injection, but has cat and EMU black box.

Any thoughts?

Many thanks.
Xantia XUD turbo lack of boost - autumnboy


Best try these who specialise in Citroen's.

www.frenchcarforum.co.uk/forum

you find an answer there.
Xantia XUD turbo lack of boost - lolingram
you find an answer there.


Thanks, I'll give it a whirl.
Xantia XUD turbo lack of boost - AlastairW
Hi. Is the throttle pedal really stiff/heavy? If so, it could well be the cable has dried out due to the heat of the engine - I had this problem on 306 wit the same engine. I squirted Wd40 into the end of the cable (the bit you can see moving when the accelerator is pressed) and the problem did not recur in the subsequent 30k miles.
Xantia XUD turbo lack of boost - Screwloose
lolingram

Do you get any black smoke when it's losing power? There's not much electronic action with this system; basically it's got a timing solenoid and the rest is mechanical. EGR problems are possible - as is a partially blocked "cat;" but neither fit really nicely with the symptoms.

Is there a DH? [or even a D8?] in the VIN number?
Xantia XUD turbo lack of boost - lolingram
lolingram
Do you get any black smoke when it's losing power?
There's not much electronic action with this system; basically it's got
a timing solenoid and the rest is mechanical. EGR problems
are possible - as is a partially blocked "cat;" but neither
fit really nicely with the symptoms.
Is there a DH? [or even a D8?] in the VIN
number?


Thanks for your help.

1) No smoke apparent in the mirror (at night especially) at 3000rpm - regime where lack of urge really begins to be seen.

2) I note that there is a sensor situated on the inj. pump that would appear to relate to throttle position

3) Explain please 'timing solenoid'?

4) Now clear that this is NOT related to engine temperature - this was bum info - sorry.

5) VIN: VF7X17E00017E2803

6) What DOES the ECU module do on this model?

Problem seemed to manifest itself after a quick engine wash down.

I once owned a Pug 205TD (nice car) that had a Lucas pump (yuck!), that lost most of its boost due to the boost pressure interface in the pump going AWOL - diaphragm I seem to remember.

Can't think of anything else relevant. This is the wife's car, and driving around locally is pretty OK - pulls well from around 1800rpm to 3000, but no real grunt as previously. As I said seems to lack extra fuel to go with the air boost.

Any further help much appreciated.

Xantia XUD turbo lack of boost - Screwloose
lolingram

Black smoke might have indicated an EGR or "cat" fault.

There may well be a "lever position sensor" on the pump depending on the exact system. [Choice of about three on this year, depending on engine code.]

The only adjustment that the ECU can make to the fuelling is likely to be the injection timing [using the timing solenoid in the pump] and the needle lift sensor [if fitted] on one injector. The fuel quantity is still a mechanical process.

The ECU's other function is mainly idle and emission-related: the EGR valve etc.

If only this were a Lucas pump with an easily changed aneroid unit diaphragm....

You say that the filters check out; have you tried a new one?
Xantia XUD turbo lack of boost - lolingram
You say that the filters check out; have you tried a new one?



A new... what exactly?
Xantia XUD turbo lack of boost - LeePower
New fuel filter & bleed the water out the water trap at the bottom of the fuel filter housing.
Xantia XUD turbo lack of boost - M.M
First I would prove you are actually getting boost from the turbo. Ideally find a gauge that will show 15psi, tee it in and lead back to inside so you can observe when driving. A quick check is to rev it up while holding one of the rubber hoses to/from the intercooler (near the oil filter) and see if you can feel the hose bulging from boost pressure.

I have had a car in with symptoms just how you describe and one of the intercooler rubber hoses was off the bottom of the rigid plastic hose. To a casual look not that obvious. Easy cure to pop back on and tighten.

David
Xantia XUD turbo lack of boost - lolingram
I carefully eliminated the fuel filter, air filter, intercooler trunking for leaks and general wiring etc,. etc.

In the end, I disconnected the throttle arm position potentiometer, and checked the tracking of the pot with a multimeter:

1) There is an open circuit between the outer two wires - brown and black in other words infinity.

2) The resistance in ohms between green (centre) and brown starts at 1.3K with the throttle arm at rest.

3) When the throttle arm is opened the resitance progresses up to 1.9K ohms

So.... I ran the engine without the throttle position pot connected. It started jst as normal and idled at 1000rpm - again normal.

I drove the card up the road and it now goes like poo off a shovel, with no smoke - at least as well as before the problem - possibly a gnat's foreskin better.

So... what does the throttle arm pot tell the ECU? I am inclined to leave as is. The problem followed a wash down of the engine, and clearly, the throttle arm pot got some water into it which has screwed it up permanently.

Anyone got any answers/thoughts? Can I leave the pot disconnected?
Xantia XUD turbo lack of boost - lolingram
The only adjustment that the ECU can make to the fuelling
is likely to be the injection timing [using the timing solenoid
in the pump] and the needle lift sensor [if fitted] on
one injector. The fuel quantity is still a mechanical process.


So if I unplug the ECU can I try it without, to eliminate this item from the list?
The ECU's other function is mainly idle and emission-related: the EGR
valve etc.


 

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