First off I know there is a similar thread to this but my engine code and type of problem is a bit different so if its better to add it onto the old thread please let me know and Ill do so. Im new here so still figuring it out, but still know that there is fantastic expertise here to draw on.
Basically I have a 2004 VW Passat 1.9 TDI PD with engine code AVB. It recently went into a garage to get the DM flywheel and clutch replaced as the flywheel basically just burst itself and damaged itself. Its the first thing to ever go on the car after some 250,000 kms so I couldnt complain but I do look after it well!
Anyways, after using it for a few days I noticed the Engine Warning Light was continuously lit and my engine felt like it had a dead turbo. I connected up the VCDS by Ross-tech and found the fault was:
17964 - Charge Pressure Control : Negative Deviation
P1556 - 35-10 - - - Intermittent
There is one other problem this appears to be causing for me which doesnt appear in any of the other posts I read in relation to this fault code.When I start the engine and start to move with the engine idling (e.g. reversing back down a hill) the brake pedal is very heavy - i.e. like it is not getting any servo assistance whatsoever - I have to pretty much stand on it. If i give the engine a bit of boot the pedal is like normal once again.
I did do a 1800RPM in third gear to red-line with the VAGCOM logging. I cant seem to upload a file here but it basically shows actual boost way below expected boost when viewed in an excel sheet. Anyways, my plan of attack to isolate the problem is as follows;
1. Check all the Vacuum hoses
2. Check vacuum in pipe to turbo actuator
3. Check movement of actuator arm at turbo
4. N75 valve check
Im handy with cars and have even change a timing belt or two but I'd really like to get this fixed as soon as I can. So basically my two queries are,
a) Is there any further items I should immediately add to the above list?
b) Is the issue with the brakes connected to the loss in power and if so does it indicate what the problem may be?
Im just not in a position where I can borrow any wastegate valve or the likes to tease this problem out part by part, and my hobby shop is a few hundred miles away. Id really appreciate any advice any of you guys could offer me on this.
PS I have the excel sheet for exp/act boost, RPM vs Mark if anyone wants to take a look i can PM it.
I should also mention that starting off after turning the car on, the turbo does appear to be working ok. However when the speedometer gets to around 100km/hr then acceleration totally plateau's out. But I think that is just the car going into a Limp mode when the actual boost and expected boost are so out of kelter. Switching off theengine and on again seems to get rid of it until I hit 100km/hr again.
The evidence you give points to a vacuum leak giving low boost due to the VNT actuator not being fully driven.
The occasional loss of servo assist makes it almost certain.
My prediction is that when they removed the transmission to change the flywheel, they let the engine hang on the front mounts. This fractures the semi-rigid "pigtail" vac pipe to the servo from the tandem pump - you may find there's a slight crack in it underneath.
If I'm right, this is another example of sloppy VAG engineering in terms of converting a basic vehicle to RHD. On a LHD B5.5, this pipe has enough slack in it to accomodate engine movement. These vehicles don't tolerate poor workmanship either.
Took me a while longer to get around to it than I had planner. But you were as good as spot on with the trouble shooting. I was looking down the turbo side of things the whole time.
Anyways took off the cover and took a look at the back of the engine and found the tandem pump and the vac hose up to the brake servo. This appeared to be ok. But the 3" long rubber 3mm hose coming off it (at what I think is a one-way valve T fitting) had nothing connected to it. Did some fishing around and found a 3mm diam. plastic pipe loose. This was running down and connected to some form of sensor/valve underneath the air intake pipe on the right hand side. Theres around 3/4 similar pipes connected to it - but Im assuming this little pipe is what supplies the vacuum for turbo control etc.
Anyways no vacuum was getting down to thsi valve to control turbo etc. Also it was leaking the vac for the brake servo. Not sure how it got detached as it is fitted to the engine along its full length. But I can see why an issue with the larger pig tailed brake hose would be more plausible.
Anyways - cars boosting it around again thanks to your advice.
The "Tee" does not contain a non return valve, so you can fit the small bore pipes in the neatest configuration. VAG don't usually do this. The non return valve is a small cylinder with a white and a black end. Watch these rubber pipes as they age - often they will split invisibly under the cotton braiding.
I wonder what a dealer would have made of this problem - new turbocharger?
I haven't been on here much lately and I know this post is really old. However, yet again your prediction was correct. The dealer told me a new turbocharger was required. We all know the type of price that was quoted.Thanks for saving me from the wolves ;)