C5 2008 (X7 ?) Turbo Fault

[MikeT]

Good news Mike, well done for the perseverance. Could you do a post that summarises the changes that helped / cured, and the ones that were red herrings?
Again well done.

Thanks Pete, though it was a team effort so I won't be taking all the blame or credit
I know threads can get rather lengthy and confusing but all the detail is here for the record so I'm not keen to repeat it - happy to summarise what I believe were the fixes.

Dash warnings Service and Risk of Particle Filter Blocking
This was cleared once Diagbox was told the DPF had been replaced.

Hesitation and flatspots
Remedied by replacing the air doser as the air heater butterfly was severely restricted.

Turbo underboost
Faulty vacuum feed to turbo cured by replacing both solenoid and actuator

Excellent - now we're looking forward to seeing your new X7's MPG as compared to the MK II!

Has anyone started a book yet in the back rooms?

I am happier than you are right now

I'm more relieved, to be honest Colin. The key's waiting for you if you'd like to take it for a spin again (though it's not currently insured).

[MikeT]

After opening, I found the old solenoid valve had a very dirty atmospheric port filter. It uses that same silk-screen type fabric found in kettles to trap limescale.
It was overlooked initially as it was blacker than a coal-face and just looked like a cylindrical plastic spacer for the rubber diaphragm when removed.

[moizeau]

Thanks for the concise version. Very interesting about the solenoid filter. Maybe something for preventative maintenance? How many miles has it done? I'm just thinking about mine as well as the 2 that operate the butterflies. As the filter blocks, full movement may not be achievable, allowing crap to settle in places that it shouldn't, and then needs replacing (or a bloody good clean if caught in time).

[MikeT]

Mileage is about 110K, Pete.
If I understand the principle of operation correctly a restricted atmospheric port will adversely affect the plungers ease of travel.
As code P0299 states, the desired boost could not be achieved for at least 5 seconds so I think this filter was pretty gunked up and would have benefited from a service some time back.

[moizeau]

Cheers Mike, when I get round to the cam belt, cam and cranks seals, I think I'll do them as well. Should be good for life then as they've done 170k miles currently.

[admiral51]

I have looked back through this thread and i still cannot believe i let a good car go with faults that were fixable but it could not be in better hands

The solenoid valve was suspected as a possible culprit way back on page 3 or 4 i think, and Mike even posted a link to cleaning it hence why a new one was obtained and has now been fitted, the access to it is horrible btw on the 2008 X7 1.6 HDI.
The solenoid valve is around £20 - £30 online and is well worth getting changed every 2 years or so.
My thinking is if we look at it as being similar to an air filter ( which the foam is ) then as you need to remove it to clean the filter then why not replace it for new ?

Stupid comparison but how many vacuum cleaners these days have multiple filters that need to be cleaned/washed for them to work as intended ?

Turbo knackered maybe not, something simple may have been overlooked, yes the fault codes are correct and the parameters recorded are outside what is expected but we all learn something new everyday

Long live The Devil Car

[MikeT]

The solenoid valve was suspected as a possible culprit way back on page 3 or 4 i think

[Cough] Page1 I think you'll find, Colin

I guess I shouldn't be but I am still perplexed that at least two professional mechanics failed to realise a tiny air filter needed replacing after 110K miles.
Not trying to be smug in hindsight, as it did take a bit of spannering and therefore a sizeable bite of my wallet to get it (and other faults) fixed. And that's after whatever expense and effort Colin had to put in beforehand. And I understand experience and educated guesswork can lead to time-saving by cutting diagnostic corners but in this case, it would have been both quicker and cheaper if the basic and proper diagnostics were carried out from the get go, imo.

Now, should I treat the Devil Car to a full service or not bother as it's running pretty good at the moment? teehee

[admiral51]

Nasty cough you have there Mike, best go see a nurse and get it checked out, no need for rubber gloves just yet

It is totally 100% your call on what you do but a cambelt change and extras i would do in your position, i have gone through all my old paperwork and invoices and i cannot find anything that relates to a cambelt change, both me and my trusted guy thinks he did replace it shortly after we got the car, we had the air con rad replaced at the same time and he remembers that because of the aggro it caused it him but we got the car in 2011 and from memory it was close to 45k miles then.
If you think the issues are solved and you think it is a keeper then when time and money suits get the lot done, even if you run it for 3 years it will probably work out pennies per week

PM sent Mike but i am really happy you think it is behaving itself
Colin

[admiral51]

Was going to start a new thread but better to keep it all together
Quick question what else does the Solenoid valve do apart from providing the vacuum for the actuator arm ?
What is part #3 in this link from a previous part in the thread, appears to be connected to the solenoid valve ?

download/file.php?id=11214&mode=view

May need admin help to make the link work correctly

[GiveMeABreak]

Part 3 is the Vacuum reserve. These solenoid units replaced the older mechanical vacuum capsules as they can give finer electronic control. There can be a few of these within the circuit generally.

[MikeT]

Excellent - now we're looking forward to seeing your new X7's MPG as compared to the MK II!

I've started a course of Millers fuel treatment, holding higher rpms for longer and generally giving it good thrashing to try and cure the cold-start lumpiness and hazy exhaust it's currently exhibiting, so I shan't be driving economically until I finish the bottle.

As it stands, over the first 50miles since the service on Monday it's averaged 47mpg which is a pleasant surprise considering the last 9000mile counter was 45mpg and the other counter I reset when I got the car, driving it to and from the workshops prior to this major service, only reached the high 30's.

[admiral51]

Mike the High 30's was what my good lady got out of it driving carefully, or as she says normal style (flat out or stopped )
Anywhere between 45-60 mpg on a daily commute to southampton and back was my norm, depending on if i was running a little late or not.

[MikeT]

60 sounds good, Colin!

[MikeT]

Don't know if it's due to Millers fuel treatment and/or me thrashing the engine every chance I get but it's no longer lumpy on cold-start idle and the exhaust smell isn't so offensive.

Compared to the estate, it doesn't pick up as well from near-idle but does seem to push harder up to (and beyond) the redline. I'm confident the turbo is boosting ok but maybe it still needs the actuator properly calibrating?
Witnessed the first regeneration yesterday so happy with that also.
I think brake pads is now the last outstanding service requirement needed on this car. I do have new pads for the estate but think the X7 has larger brakes so won't fit?

[MikeT]

Presented for it's first MOT under my ownership today and pleased to report it passed with no advisories (a credit to the previous owner, I'd say).
The tester complimented it's condition telling me it's "really clean underneath" and the emission test results were "very good". He seemed to be particularly impressed with the engineering/build quality of the front-end (suspension/steering) too for some reason.