Finally admit defeat C5 2.0 HDI - someone help!

[mark6535]

Right here goes a long story, first off though I am a mechanic but HGV not cars.

Driving home from skeggy 3 weeks ago and all of a sudden car lost power, ESP/ASR system failure warning come on the dash...all of a sudden it gave me full throttle for a few seconds then died.
Simple I thought...turbo's gone.

Got it home and I had faults: (on Delphi)
P16A0 - detection of oil after engine cut off
P2566 - Variable geometry turbo.

I checked pipes, boost solenoid, vaccum system ..all ok, actuator wasn't moving on turbo.

Engine out...turbo sent away for testing, came back as absolutely fine. With repeat sensor giving correct info (apparently).

So whilst engine was out I checked all plugs, vaccum lines again. Put it down to maybe just one of those things.

Reassembled and it sounds like a diesel supra (pssst...tutututu).

Now with Diagbox I had:
P149C
P0238
P2566

Selected "new turbo fitted, new MAP sensor fitted"

Followed a turbo learn in procedure found on here:
For lower limit idle when hot, ignition off, lock car, Ignition on, job done.
Upper limit drive in 3rd from 1000rpm and accelerate hard.

Didn't work the first few times but today when the usual dash illumination happened and I ran diagnostics only fault P0238 remains (weird)

MAP sensor replaced, still the same, checked loom, All ok.

Live data does show the requested turbo values and repeat values being different and it still sounds like a petrol with a blow off valve.

Am I missing something here

Appologies if I've missed any details out...5 days on this and my head is fried.

Just to add I've popped the grey cap off of the old boost control solenoid and spotted a small Allen key adjuster. Could this be the answer to my problems?

[mark6535]

Finally making progress, I found that when I wound out the Allen adjuster on the boost control solenoid I replaced by 1 turn, the pssst tutututu stopped, one more full turn out and it sounds and drives great....UNTIL 3rd gear full load. Now it shows under boost fault.

Wound it back in a quarter of a turn...over boost.

So the plan is tomorrow to wind it out another half a turn (2 and 1/4 in total). Reset the turbo values, test drive and keep winding it in a smidge at a time. It's the only logical idea I have left

[xantia_v6]

I think it unlikely that changing the solenoid valve calibration will really fix your problem. The ECU "learns" the calibration of the valve (and the actuator it controls) by making long-term comparisons of the requested and actual boost.

How different are the actual and requested boost pressures? Are you sure that you dont have a loose or split boost pipe?

[mark6535]

So today I disconnected turbo actuator pipe, and by sucking on it I can see the turbo repeat value going up smoothly. So I can rule out that this part is faulty.
I've also worked out that screwing the adjuster on the boost control solenoid almost all the way out, I can get the required boost pressure and actual boost pressure to work in sync perfectly....but it throws up a fault because turbo repeat signal doesn't match requested turbo position.

And then by screwing it back in to where it was i can get the requested turbo position and the repeat signal values to match up and work in sync perfectly. But then it throws up an overboost fault because requested boost pressure and actual pressure are miles apart

I've refitted the old control solenoid, checked as best I can for blockages or leaks on vacuum circuit. I even popped out the dipstick incase the crankcase was pressurising from vacuum pump. Still the same.
I've got a vacuum gauge arriving tomorrow so I can check actual pressures, but apart from this I'm at a loss.

I'm 100% sure boost pipes are ok as I checked them all when engine was out. In terms of how far out the pressures are I'll plug back in to it shortly and write down the figures

[mark6535]

Last readings were:
P0238 - Manifold pressure sensor - maximum charge pressure exceeded.
Engine RPM - 2752
Turbo reference value - 2.32 bar
Turbo pressure measured 3.01 bar

This was with boost solenoid back to how it is as standard, with reference value and repeat signal values working in sync.

[bobins]

Was the replacement MAP sensor a genuine one, or a Eurocarparts special ?

[mark6535]

ECP special I'm afraid. So was the one that came off of it as it is identical. Do you reckon it would be worth comparing the pressure values at say 2k/2.5k/3k rpm with this sensor against the old sensor values?

[Dormouse]

yes - check the values
this has been a real mare of a problem
if nothing else it will confirm if the two parts agree and conform

[bobins]

I'm hesitant to send you on a wild goose chase, but ECP don't have a great reputation on here when it comes to....ummmm.... lots of things In an ideal world you'd be able to borrow a known working one off a mate's car to see if that's where the issue lies without committing more money to it.
If it were mine, I'd want to be absolutely sure that the MAP sensor is 100% OK before delving deeper.

[mark6535]

I agree, this has been a headache from start to finish. Luckily my friend has a 2013 C5 x7 exactly the same as mine, so if by Monday I haven't managed to sort it he has agreed to let me borrow it to compare values and swap parts, rather than throw the parts cannon at it...and my wallet .

Right soon as the little one has gone bed I'll get the laptop back out and take readings from both MAP sensors and post them. Annoyingly whatever the fault is is also probably the same fault it had when it broke down and before I ripped the engine out

[mark6535]

These are with the new map sensor.

[mark6535]

I'm having trouble adding pictures.
Basically low revs all seems normal.

Get to say 2300rpm upwards and that's when overboost starts...with both new and old sensors being pretty similar.

2300rpm,
turbo reference 1160mb
Measured 1314

2700rpm
Turbo reference 1195
Measured 1605

3000rpm
Turbo reference 1250
Measured 1525


Throughout this the turbo position and repeat values start around 80% at 1500rpm and by 3000rpm they are both down to 55%

[Hell Razor5543]

To add pictures you need to have selected the "Full Editor & Preview" option. Then you have the ability to upload the pictures. The basic editor (where I am typing this) does not.

[mark6535]

I keep seeing the phrases "adapt/learn/update parameters" realistically what are the chances the ECU will adjust for less turbo in the future

[KennyW]

What engine is in your car and year ?

Kenny