Black smoke and turbo lag

[redb7avant]

Hi everyone, I'm new here so excuse me if this is posted in the wrong place.
So I bought a 2006 A4 Avant S-Line 2.0TDI 140 in November last year. When I bought the car it had been sitting for a short while (2 months or so)
Since then, it has been producing more and more black smoke, but the turbo range has stayed pretty much the same from what I can remember.
The car comes onto boost at about 2200RPM, and then the smoke will go away, but below that there are plumes of black smoke coming out of the exhaust. At first I dismissed it as normal due to the engine not having enough air from the turbo at these low RPMs to burn the fuel but it's got really bad now.
At the moment it is so bad that after about 3 days or so the whole left rear of the car will be significantly blackened by the amount of diesel smoke that comes out of the exhaust. I know the TDI140 engines didn't have a DPF but this is excessive for any stock engine DPF or not.
Currently when cold the car feels like it doesn't have a lot of power, for example it's tricky to do a hill start on a steep hill without almost stalling the engine (manual trans).
It's not like I'm doing short trips for carbon to build up either, I have done 7 thousand miles in the car now, and just last night I took it 500 miles to West Sussex and back.
Most of my driving is motorway, but I do have a spirited driving style on the smaller roads, so I don't think anything could've built up in the engine due to not driving it hard enough etc.
The car has a CEL on (code P21o8 'Throttle actuator control module performance) so this could be a related fault.
Has anyone got any ideas as to what the problem may be?

 

[LawrenceH]

I’d start by checking for boost leaks. Check all intake pipes from turbo to inlet for splits or joints not seater correctly/clips loose etc.

 

[redb7avant]

Hi mate,
I had a brief look in the dark. There is a potentially loose coupling where the pipe from the top of the intercooler goes into the engine. It can move and twist a bit. Not sure if this is normal or if this is actually an incorrectly seated pipe causing a boost leak.
The area around this pipe is also excessively oily too.

 

[LawrenceH]

Sounds like it could well be leaking there, see if you can tighten the clip or replace it if it’s knackered.

 

[DieselJake]

If it's where I think your talking about the connections are quite common to go bad, haven't got any pictures to hand but some people change the clamps on it and use rubber band type things if the two halves are coming apart or for more of a permanent fix Darkside has a metal pipe that replaces it but I'm not sure if they sell it separately or just as part of an intercooler kit.

I have an upgraded side mount intercooler kit kicking about but I'm not sure if any of the pipes will be any good to you.

 

[Gazwould]

As above all the joints are poor and can be firmed up with a jubilee clip and cable tie method .

 

[Dan_Avant]

As stated above. If you’ve got oil around a joint that is usually a sign of a leak in that area.

Let us know if that fixes or helps towards fixing your issues mate.