Diesel whiz needed! Narrow power band and smoke!

heath robinson · Post by **heath robinson** » 27 Oct 2004, 03:48

Hi
95 1.9 TD xantia
The car will travel fast enough. In Europe comfortable at 100mph, didn’t push any further, though would probably have gone further. However acceleration is naff after around 3750. The car has a spurt of power around 3000 to 3750 and then drags round to just under the red. There is also a cloud of smoke left behind on the odd time I do use full throttle to accelerate. I usually accelerate in a gentle way, so don’t often push the car, partly as it only does 37mpg rural and urban combined, and there is no point pushing clouds of fuel into the environment.
Could the car be over fuelling? Would this muck up combustion therefore make post 3750 such a drag?
Does the pump need adjustment to reduce fuel input?
Is the turbo duff? How would this explain the smoke?
More info:
The throttle cable is fine and fully operates the pump.
I have used injector cleaner to no obvious effect.
The engine does not use oil.
The car has done 111k and appears to have been well looked after for at least the last 5 years from records.
I have to say my 214k non turbo zx was fab by comparison. Worst I could get was 46 mpg!
Any pointers very gratefully received
regards

Kowalski · Post by **Kowalski** » 27 Oct 2004, 15:12

It looks like it could be suffering from a blocked exhaust, but you could try checking the air filter first.
The fact that there is a spurt of power indicates that the turbo is working, the fact that it produces it at 3000 rpm means it isn't working entirely properly, and then there is the fact that it fades early.

TomH · Post by **TomH** » 27 Oct 2004, 15:22

If you drive it gently all the time it might need a bit of an Italian tune up to clean out the cobwebs!

G4EIY · Post by **G4EIY** » 27 Oct 2004, 18:19

Hi,
It sounds like you may have got what they call "A Lazy Turbo".
This occurs when the car is never given a good thrashing, to clear out all the crud.
The turbo gets all coked up, and consequently does not spin at the required rpm.
You may be able to clear out some of the crud, by giving a good Italian Tune up as mentioned, but the best way is to dismantle the turbo, and clean all the internals, reasemble and re fit...
To test you need a turbo boost gauge, then you will be able to obtain the pressure at various rpm and load levels your turbo is producing, compared to the published data.
Cheers

Robin · Post by **Robin** » 27 Oct 2004, 21:33

Acceleration will fall off after around 4k rpm but the obvious areas for checking are the air filter and the injectors. Depending on the use the engine has had around 100k is good time to rpelace the injectors. The internals begin to suffer and give inaccurate injection rates and timing can suffer marginally too as a result. Choked exhaust is possible. Does a 95 have a cat fitted? If so it is possibly ready for replacement too.
The symptoms all point to high air volume problems either into or out of the engine.
Breathing is vital for diesel. Robin.

pete_wood_uk · Post by **pete_wood_uk** » 27 Oct 2004, 21:40

If it cruises "comfortably" at 100mph then I'd be surprised if it's the turbo stuck. On the other hand, I can't think what else it could be. I had the injectors on my '97 TD removed, cleaned and reset a few years ago, at about 80k miles, which crisped everything up a bit, but I wasn't suffering symptoms as bad as these beforehand. (tenner an injector, money well spent, but that was for cash by an old family friend, so "high street" prices may differ).
Cheers
Pete

madasafish · Post by **madasafish** » 28 Oct 2004, 01:15

Do your front disk pads last over 40,000 miles? (or had you to replace the disks first due to corrosion?
If so you drive far too gently and should be much more brutal with the accelerator.

arry_b · Post by **arry_b** » 28 Oct 2004, 04:22

uhn113x · Post by **uhn113x** » 28 Oct 2004, 13:16

I think what MAAF is saying is that if you propel your passengers violently towards the windscreen every time you slow down, like bus drivers do, then your car will go faster.
No, I do not understand this, either [?]

madasafish · Post by **madasafish** » 28 Oct 2004, 13:27

no what I was trying to say was:
If your driving style is sedate and careful and you never drive hard or rev hard or accelarate hard, the engine will coke up with carbon
A sign of the above is little use of disks leading to corrosion:-)

heath robinson · Post by **heath robinson** » 29 Oct 2004, 01:00

Hi, thanks to all for your time and pointers.
the air filter could be a problem. Although new, I bought it from euro carparts and it is unbranded so who knows whether it is sub standard.
I probably do drive a bit steady these days. My 998 imp had an R21 cam, which meant it came on cam at 6k; however, those days are gone and I now live in the 2-4k bracket. However, I have blasted the car on full throttle in second and third in an effort to exercise the turbo. The crap comes out, but even after a couple of drags at maximum revs the car still does not have the power 3750 to red line that I would expect. It is slower than my old zx non turbo.
Given the cost, I may try wynn’s dp3 cleaner, unless people know better, and then look towards a new set of injectors. I guess I could always hang on to them if they don’t need changing. (I like the 1.9 engine and will I think stay with it for some years in this car or others)
The turbo boost gauge sounds like a good idea. I take it this is a diagnostic tool that you would temporarily fit while running the car through the gears? Is a turbo strip down a day job? Do I need to buy new seals or other bits to strip and rebuild a turbo? would a duff turbo link with poor fuel economy?
No cat fitted until 96 I believe. It does though have an asthmatic feel to it. Can an exhaust without cat block?
Haven’t had the xantia long enough to see how long pads last. I’m certainly not hard on them, though agree with you that they need to work hard from time to time to stay healthy. I think in my zx non vented I used 3 sets in 85k
Look forward to your thoughts
regards

oilyspanner · Post by **oilyspanner** » 29 Oct 2004, 01:34

Your Xantia is an indirect injection diesel and produces most of its power in the midrange, IDI diesels dont rev much past 4000 anyway, are you driving like a petrolhead?
Stewart

Robin · Post by **Robin** » 29 Oct 2004, 02:10

I am interested in your comments about the Imp and its response to the cam. If this experience is guiding you to expect an increasing power output with rising engine speed to the red line then ...... Diesels don't have the same power characteristics/response as a petrol engine. Acceleration is a product of torque not outright power. So your maximum acceleration will be from the turbo coming in at around 2300 upto around 3500 or so. Under these conditions flooring the pedal will actually hinder the acceleration by causing overfuelling. Backing off can often give you an increase in speed. The way to get the best performance is to practice balancing the depressing of the accelerator so that your foot arrives at the carpet just ahead of the engine hitting the red line which you wouldn't do anyway having changed up at around 3k to 3.5k rpm.
Try this in second gear and third for practice. From a rolling start with practice the Xant will give quite a few cars a fright in terms of acceleration in second and third.
Best wishes, Robin
P.S. I used to race against Imps in an Anglia. Gee they were quick!

ghostrider · Post by **ghostrider** » 29 Oct 2004, 03:52

yeah but only til the headgasket blew ! [:D] [:D] [:D] [:D] [:D]
________
Magic flight launch box

Richard Gallagher · Post by **Richard Gallagher** » 29 Oct 2004, 04:28

I had an 'under-performing' Xantia TD, which when the engine was hot, really lost performance and pumped out black smoke.
After checking everything and I mean everything, changing pump/injectors etc, it turned out to be the air filter intake ducting had broken up thereby allowing hot air from the radiator, intercooler and aircon condensor to re-enter the intake ducting rather then cold, and therefore denser outside air in. Check under the air filter that the intake ducting underneath has not disintergrated.