Discovery 2 boost drop

Hi I have a stage 2 remapped discovery 2 td5 I have a electronic boost gauge plumbed into the inlet manifold I have been running the car at 1.4 bar on the boost gauge it has been fine for over a year now tho it will boost upto 1.4 bar then drops down to 1.2 and just sits there any ideas why this is happening I've changed all filters cleaned map sensor maf sensor is deleted replaced waste gate modulator changed turbo checked for boost leaks I have silicone boost pipes couldn't find any leaks it boosts fine then it just drops and sits there it use to pull at 1.4bar right through the rev range any input appreciated

Also oiled waste gate dosnt stick atall

Collapsed intake tube? Invisible of course.

Wich one are we talking about mate the one with the pcv valve on it ? Cheers

Craigevo92 said:

Wich one are we talking about mate the one with the pcv valve on it ? Cheers

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Technically any of them, delamination can be a problem, but if yours are new and silicone I'd look at any others first.
Also make absolutely sure all jubilees on them are on properly and tight.
Could also simply be the turbo isn't generating the boost it used to. Check oil feed to it, but if it really had a problem you'd hear it, I'd a thought.
Have you cleaned the intercooler?
Have you altered the setting on the waste gate which conventionally is at 13 threads I believe?

Iv changed the turbo still the same adjusting the actuator on waste gate turns the boost up to 1.5 but it still drops back to 1.2 there was oil around the old turbo so could of found it's way into intercooler I was thinking maybe fuel pump might be the problem I did buy a cheap no brand one a few months back could the fuel pump cause this type of problem ?

Craigevo92 said:

Iv changed the turbo still the same adjusting the actuator on waste gate turns the boost up to 1.5 but it still drops back to 1.2 there was oil around the old turbo so could of found it's way into intercooler I was thinking maybe fuel pump might be the problem I did buy a cheap no brand one a few months back could the fuel pump cause this type of problem ?

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Sorry but i have no experience of this, but keep with it, someone with more knowledge of boosting boost will come on.
But I would say that the turbo runs from the exhaust and simply compresses the intake air, so the reading you are getting has nothing to do with fuelling as that happens after the point you mention, i.e. in the head. so I doubt the fuel pump has anything to do with it.
The only other thing maybe could be to do with the ECM reading the boost and thinking you are at risk of overfuelling, and thus putting it into limp mode. This I have had when my wastegate lost its two bolts, But you would really know about that if it happens as the engine really loses power.

disconnect the waste gate actuator so waste gate doesnt operate

jamesmartin said:

disconnect the waste gate actuator so waste gate doesnt operate

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Yes did that mate it boosts straight into overboost and cuts fuelling

The boost is also controlled by the ECM based on sensor readings so a live data log from a drive is necessary

Craigevo92 said:

Yes did that mate it boosts straight into overboost and cuts fuelling

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not a turbo or fueling issue then its the control mechanism either soft ware or boost sensor

What sensor controls the boost the map on the side on intake manifold ? would it be worth replacing that my mate has a spare that we took off his old engine

Craigevo92 said:

What sensor controls the boost the map on the side on intake manifold ? would it be worth replacing that my mate has a spare that we took off his old engine

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boost pressure sensor on the inlet manifold

jamesmartin said:

boost pressure sensor on the inlet manifold

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Thanks for your reply Il replace sensor tomorow and give you a update

Another important sensor in boost control is the AAP sensor(in the airbox) and the crank sensor is involved too cos if as you said the MAF is deleted the fuelling is based on MAP/rpm relation and the boost on MAP-AAP difference, as i said the only certain way to see what's wrong is a live data log

So I replaced map sensor still the same when I unplug the aap sensor it's still the same does that mean that's my problem or does unplugging that not make any difference any way thanks

With faulty/unplugged AAP the default is limited boost but unplugging and replacing sensors based on guesses is quite feckless, i'll not repeat again the correct way to diagnose this as i said it twice

sierrafery said:

With faulty/unplugged AAP the default is limited boost but unplugging and replacing sensors based on guesses is quite feckless, i'll not repeat again the correct way to diagnose this as i said it twice

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Thank you for your reply if I had a way of reading the live data I would luckily map sensor I got was off a old engine my mate had so not cost me anything yet

It was no different atall with the aap sensor unplugged so think I will start there by replacing that and go from there

Is your's Eu2 or Eu3 engine ?