Any Ideas - Audi 2.0 2005 TDI Poorly

[GTIMKiiJODE]

Is there any TDI whizzes on hear - searched lots of forums for clues but to no joy - endless threads hat never tell what fixed problem.

My A4 2.0 140 tdi - driving along motorway - put foot down and no power at low revs with lots and lots of black smoke - after alot of chugging and chuffing when you get the car over 2000 rpm it clears and turbo kicks in and it is fine. When ticking over its also fine. No engine management light.

Diagnostic codes read were
16683 boost pressure not reached -
16785 EGR Valve

17055
17057
17058 all three glow plugs

Erased faults and drove - only code to re appear was 16683 boost pressure not reached.

My local garage replaced the boost pressure sensor - but car still has same symtoms.

No power at low revs with lots of black smoke. after 2000 rpm runs fine. I have to dip the clutch and try and clear problem so lots of revs and then slip clutch a little in low gear - clouds of black smoke though. It happens every time i pt foot down at low revs.

Apologise if this is the wrong forum but had some top quality advice from this forum from previous GTIs. Thanks in advance. Cant help feeling that diesels are troublesome - especially vw/audi and v expensive. Does this sound like turbo failure  . I have checked all pipes and none appear loose and no leaks. When turbo spins it sounds fine. Is black smoke - excess diesel. Ive been told burning oil is blue smoke. This smoke is defo pitch black.

[adi]

Have you cheked all the vac pipe's, the one's that run over the top of the rocker cover can some time's melt and cause vacume loss, there is also a diafram unit on the right hand side of the rocker at the front that can fail would be worth checking it is holding pressure and i would remove the egr valve they can fail and be stuck open, is there any hissing on boost possible split intercooler or the right hand boost pipe from the intercooler to the turbo can fail there are modified one's available.

[GTIMKiiJODE]

Adi thanks

I havent looked really closely at the vac pipes - i will look closer in the morning.

There is no hissing at all.

[GTIMKiiJODE]

Replaced EGR valve (£273) and glow plugs today. EGR was full of total dirt and valve was stuck open.

However after this -

Cars now overboosting and going into limp mode.

Going to change ? boost pressure sensor monday as couldnt get one today.

Hope all that black smoke and open EGR hasnt nailed turbo - i have read the variable veins on turbo get stuck open and this can cause overboost.

[Dannyavw]

Replaced EGR valve (£273) and glow plugs today. EGR was full of total dirt and valve was stuck open.

However after this -

Cars now overboosting and going into limp mode.

Going to change ? boost pressure sensor monday as couldnt get one today.

Hope all that black smoke and open EGR hasnt nailed turbo - i have read the variable veins on turbo get stuck open and this can cause overboost.
What faults are logged after you replaced egr valve?

[gtibarnesy]

sounds to me like the veins on the turbo are sticking.  not that unsual. They can stick either end of the scale giving you boost low down when pulling away or higher up the rev range when you want to accelerate at cruising speeds.

[GTIMKiiJODE]

OK Problem sorted - thanks to Audi Northampton.

Following EGR replacement - All black smoke stopped but still no power at low revs.

Still getting fault code16683 boost pressure not reached. Audi said that the boost pressure valve was faulty - this didnt add up as I had already replaced this originally - however with an after market one (Non genuine).

Audi Northampton recommended replace boost pressure sensor with a genuine one. They did this for me and the car is now sorted. They also seviced and replaced three glow plugs. And now the car feels better than it ever did before this problem started - really smooth throttle response. The turbo kicks in much earlier and smoother I cannot believe the difference ??

Do they perform software upgrades to the ecu at dealership service - car feels so so different - maybe EGR and boost pressure been on the way out for a long time. Never taken my car to dealership before as scared of cost - but turns out i'm v impressed.

Thanks for all advice - much appreciated. 

[adi]

Glad you got it sorted you can't beat main dealer service and the prices are ok, i work for audi and see many back street garage mistakes and for your question about software update's yes they are performed if req.