A6 2.7 Bi turbo trouble :-(

[layrway]

Hi all i have just recently purchased a 1999 A6 2.7t and i am having terrible trouble with it.
When your driving it normally its great, as soon as you put your foot down and it starts to boost it shakes, jerks and makes a kind of clonk clonk noise from underneath.
it feels like its hoding back/missing, but when ticking over or revving it feels fine.
when the first turbo kicks in it feels great its just when you start to pick up speed or sitting at any speed and put your foot down it all goes wrong.
i have checked the obvious like the air pipes big and small, im just totally lost if anyone can help.
thanks

[Peter D]

Is this an AJK engine code it is on the ID label in the spare wheel bay.
You say when one turbo kicks in. May be that is you problem, theay are supposed to both come in together. One turbo may be at fault or it's control. Regards Peter

[mad-for-tar]

First of all the biturbo engine is not a sequential turbo design, both turbos are the same size and each feeds one bank of 3 cylinders so there is no such thing as the first turbo kicking in and the other following, they both work in tandem.

This could be anyone of a multitude of things causing this problem. First thing to do is get it scanned using VCDS or VAG-COM and see what error codes are logged in the engine ECU, only then will you be able to start looking in specific areas for the particular fault. these engines have a quite complex turbochaged air control circuit and you would need to understand what does what when you go looking for problems.

Second thing I would advise is to get a pressure test carried out, this will pinpoint any leaks in the charged air circuit that you may not be able to see yourself. Some good guides to this here (http://www.vaglinks.com/Docs/Audi/C5/AllRoadFAQ.com_Audi_C5_2.7T_PressureLeakTesting.pd f) and here (http://www.vaglinks.com/Docs/Audi/C5/2.7T/2.7T_Pressure_Tester.pdf) on how to do so. Also if you want to know a little more about the systems of this engine, have a look at this document here (http://www.ibiblio.org/tkan/audi/2.7Biturbo-SelfStudy.pdf), its a great insight into the ins and outs of the V6 BiTurbo engine.

Spark plugs have a habit of coming loose on these lumps too, twice I found loose plugs in mine so might be worth checking they are secure. You may also have problems with ignition coils or the amplifiers.

MAF is a known weak point also as is the N75 valve. Change out the divert air valves also if not done before, these are more commonly refferred to as 710N's (as standard items are often changed out for the 8L S3 items, 710N being the end of the part number).

Get it plugged in anyway and get it scanned for fault codes, post them up here and someone will have a better idea on where to point you then.

HTH :)

[chapmac41]

Hello
I've just picked up your 2.7 Biturbo-SelfStudy.pdf from a previous posting on the VWAUDI Forum.
Is there a similar document for the Gearbox options?
Mine is a 5 speed Tiptronic on a 02 plate 2.7T Biturbo Quatro Avant.
The gearbox is giving me concern.
Cheers
Chapmac41