MOT fail.

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pauljordanie
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MOT fail.

Post by pauljordanie »

1.6HDi, DV6TED4 engine. The car failed MOT on excessive smoke. It off the scale. The engine was hot and I had dipethane already added. TBH you can see plumes of black smoke sometimes in the rear view mirror. I'm not sure where to start air filter is new and no leaks on inlet side. There is oil building up in the air intake chamber after the turbo intercooler. It's on 260000 kms, drives fine and plenty of power. In addition if I floor it and hold revs above 3k I get a bit of hesitation and sudden drop in power. It's a bit of a splitter. No belching of smoke under high rev conditions.

Where to start?

Thanks Paul.
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GiveMeABreak
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Re: MOT fail.

Post by GiveMeABreak »

A diagnostic - something isn't right - but without pre-empting a diagnostic, it's possible you have crud in the intake manifold that could be restricting airflow - leading to the ECU compensating and making it run too fuel rich. Are you rev-limited to 3000RPM? That's the usual limit if the ECU is putting it into backup mode until the problem is fixed, but I would of expected the engine warning light to be triggered if severe enough. If you cruise control disengages randomly, that's another sign the engine management is reducing power under a backup mode.
pauljordanie
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Re: MOT fail.

Post by pauljordanie »

It's not rev limited to 3000 revs and EML doesn't come on. There is oil in the inlet chamber after the inter cooler as there is evidence of oil dripping on aux belt. I've scanned with lexia and nothing in there. Since it thrutches/ misfires/power dies at higher revs about 3500 I'm thinking more along injectors need doing. Am I justified thinking along those lines??
admiral51
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Re: MOT fail.

Post by admiral51 »

Does it have the double butterfly air doser ?
Does it appear slower to get up and go, it make have been doing it for a good few months just not noticeable over time.
If it has the turbo solenoid valve the filter on it may need cleaning/replaced.
Anything over 3500 revs do you get the flat spot, foot down and nothing, lift off and revs again ?
Just asking as they are similar symptoms that i had in my old C5 X7 that Mike T is now enjoying

I and never had the EML light on although in later Lexia tests it did show up turbo under boost and it would disable the cruise control/speed limiter
pauljordanie
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Re: MOT fail.

Post by pauljordanie »

I replaced the turbo solenoid valve about 3 months ago as I had a couple faults on ECU air flow fault and something else. Power is there across the range but stutters above 3000. It has double butterfly doser
admiral51
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Re: MOT fail.

Post by admiral51 »

You can remove and clean the air doser, but if you have the stuttering then i would suspect that as being the cause.
Will link to a post that had similar problems with the same engine.

May not help but the symptons seem to be what i had This One
MikeT
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Re: MOT fail.

Post by MikeT »

Try replacing the small o-ring on this air intake pipe.
As you can see from this pic, there's excess oil being drawn into the intake because it's no longer providing an airtight seal.

I'm not saying this is your problem but for a few pennies, it's worth doing anyway.

Image
pauljordanie
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Re: MOT fail.

Post by pauljordanie »

I cleaned out the doser today and there wasn't much oil/crud in there. I also replaced the rubber seal in the pic. I also did some snooping with Diagbox and lexia. Miles since regen is 0. Average distance between last 5 regens is 0. Fluid says 3000...could it be that it's not done a regen and dpf is bunged up I wonder?
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GiveMeABreak
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Re: MOT fail.

Post by GiveMeABreak »

That certainly doesn't sound good. On the basis of what you have reported there - it would seem that it is not injecting any additive from the remaining quantities and also the distance between regens / average. If it's not regenerating it will start to clog and my concern is, that when the filter gets to anything like 70% + full it will not be able to regenerate, necessitating a deep clean or replacement, so quite important you get to the bottom of it.

Are you certain there are not other fault codes after undertaking a Global Test?
pauljordanie
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Re: MOT fail.

Post by pauljordanie »

No faults recorded in ECU other than clutch position switch and a fault I've had for ages - fault comms between ECU and ABS ECU. that's intermittent and only occurs periodically and when travelling at a certain speed. Other than that nothing.

What's the trigger for adding the additive? Is there a switch on the filler flap? How can I test this?
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Stickyfinger
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Re: MOT fail.

Post by Stickyfinger »

It is a magnet "switch" that lives on the fuel filler pipe just below the filler hole. A bit of a pig to get the wires around the tank on the Mk1-2......not sure about the X7


Part No 20
Capture.JPG
pauljordanie
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Re: MOT fail.

Post by pauljordanie »

Ok, so if open close the filler flap additive should be added. Is there a counter I can access via lexia to see if ECU see's flap open and close?
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GiveMeABreak
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Re: MOT fail.

Post by GiveMeABreak »

This isn’t an X7, it’s a C4GP.

No it doesn’t rely on this alone. It has to determine whether any fuel has been added or not. It is a combination of detecting the fuel cap being opened and also measuring whether fuel has been added from the previous quantity or not. But there would also be a fault code if the plug detect harness was faulty.

Sometimes the additive pouch (if replaced recently) may not be operating or may need to be primed.

This is the correct diagram for your vehicle:
106A5295-3EB6-481B-9663-CF21516AF866.jpeg
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Stickyfinger
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Re: MOT fail.

Post by Stickyfinger »

my bad...sorry, brain freeze (understandable at the moment)
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GiveMeABreak
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Re: MOT fail.

Post by GiveMeABreak »

👍 No worries Alasdair