2,5 tdi AKE running rough when warm.

Hi and welcome to VWAUDI uk, also velcome to the exclusive " 2,5 tdi barks when hot" club !;) Lets hope your membership in the first club will last a good bit longer than your membership in the last one ...
I assume you,ve checked out the COI ( maybe also tested to adjust it off both ways ? )
Next thing I'll do is to pressure test the boost system again then pull all of the inlet/ boost stuff and the exhaust system out of the car and take a very close look at it

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Originally Posted by nedge2k

Chalk up another victim to this issue!

I've just replaced cams/valves/etc/etc after one of the bolts holding the N/S rear cam belt guard worked loose and destroyed the cam pulley.

I had the barking issue before but though it was because the needle lift sensor had failed and my cams were worn.

Well, I've fixed all that and when she's cold, the engine is smooth as silk and pulls well but as soon as it gets up to temperature, BARK!

Thought i'd have a read around before I start figuring out why!

FWIW, mine is a 2002 AKE Allroad BUT the engine is from a 1999 AKE A6. No idea how much of the engine is 1999 but I'll be checking the IP!

The only other thing with mine that none of you guys have mentioned is that sometimes, I'll get a hesitation, followed by the ESP, ABS and suspension level warning lamps and the suspension will drop down to level 2 - I think this may just be another issue unrelated to the barking though.

One of the many useful bits of info in this thread was about the two pumps in the tank. When I primed the IP, just tried to manually power what I thought was the lift pump (according to Elsawin) but no fuel got to the filter. I now realise this was probably the baffle pump, so I'll be checking my lift pump is working as I should have one...

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Just noticed the last part of your post, There are only 1 pump in the tank but the layout differs. Its eighter used as a baffle chamber pump or as a baffle pump/lift pump or as a sole lift pump where the returns makes the baffle chamber fill up.
@ Matkring-Good to see you're still around ! are your car still running good ? Did you find out exactly what happend when your engine decided to run on all 6 cyl ;) ?

So with static timing it was -1 (late) and took a while to start when hot. I can't remember if the bark was as bad because I quickly adjusted it. Now it's...

Early: 15.4°, 17.4%
Late: 2.6°, 100.2%

I checked measuring blocks 13 & 14, all no more than +/-1.

All measured at 90°C+

Is it worth readjusting to 1.8-2.0°?

I also logged measuring blocks 10, 11 and 15:

Attachment 25178Attachment 25179

If your late reading is + 2,6, the COI is too advanced. Correct it to 2,0 ATDC, also minus

A lot of people get thrown by the ATDC and minus part as the manual says 2° ATDC ± 2° and VCDS shows it as minus BTDC. If you set it at 2° but BTDC, you are 4° off of the optimum. Using the VCDS TDI timing graph stops you making this error.

Unfortunately I only have vcds lite and the AKE is not available in the TDi timing graph.

So to be between 0-4° ATDC, when VCDS shows late I want to be 0 to -4°, ideally -2° BTDC?

If so, why did it take so long to start when hot at -1? I'm now at +1.6° and it seems better.

Good question, and since mine was/is exactly like that I had the COI set to +1 degree. Take a good look at the transparent diesel hose and look for air bubbles, starting when hot is much better since I got rid of the air.
And right, -2 BTDC is right

Make sure that both your injector return lines are fitted with non return valves. Some cars did not have them but even cars not originally fitted with them seem to benefit.

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Originally Posted by ametlib

Hi and welcome to VWAUDI uk, also velcome to the exclusive " 2,5 tdi barks when hot" club !;) Lets hope your membership in the first club will last a good bit longer than your membership in the last one ...
I assume you,ve checked out the COI ( maybe also tested to adjust it off both ways ? )
Next thing I'll do is to pressure test the boost system again then pull all of the inlet/ boost stuff and the exhaust system out of the car and take a very close look at it

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Just to keep my small, humble tread alive I'll write a few words about my new theory ;)
As I've said earlier, this car have exhaust sound when it's running ok and no exhaust sound when it's running sluggish. I think the turbo itself is what's clogging up the exhaust. Every graph I can read out of the ECU looks like from a perfect running engine, also the boost graph, so
how is that possible ?
If you open an VNT turbo you'll see that when the vanes are pointed in the max boost position ( N 75 nearest to 100 %) , the openings for the exhaust to escape are almost closed. So what I will look for is a boost leak or exhaust leak ( egr + pipes),
anything obstructing the inlet/ boost system or clogged up exhaust, that means anything that will make the ECU run the N75 more in order to make the actual boost follow spesific boost.
Meaning E.G if there are a small boost leak,
the ECU will still manage to follow the boost map by running the N75 more, BUT, in the same time it's biting it's own tail by closing the exhaust system......
Will ofcourse also check that the MAP is reading correct by using an external gauge.

I made a boost leak tester for mine using a section of 50mm round nylon bar, drilled a hole through the center, fitted a schrader valve from a tyre and then used an air compressor with a tyre inflator.

If you have access to a lathe, I would suggest a larger diameter at one end and then turn down the rest to form a lip, or maybe a series of dome-head screws around the top - mine popped out at 30PSI :P