A6 2.7t , 2000 with overboost code...
 

I am looking for tech papers on the procedure to pressure test the intake system on a 2.7t
My mechanic is arguing with me that there is no need to do a pressure test because the fault code was "overboost". Apparently leaks can cause that too!

In short: I am trying to justify doing a pressure test even when we have that code. Expert opinions are welcome. s4master1 has provided me with very good information and i wish to thank him.

Present problem with my car: When accellerating from 3500 rpm,apply full throtte the torque response is coming and going aprox ounce per sec. up to 4000 rpm and it than goes flat. It takes a very long time for the engine to reach the 6000 rpm range even in second and third gear. I was advised earlier on this forum (thanks guys!) to look for a leak with such symptoms. I totally agree with this. But my mechaninc will not cooperate. He gave me all kinds of excuses. Here is roughly what he says:(after spending a total of over 4 hours "investigating" the problem:

1) It can't be a leak because of the "overboost" code
2) He admits that if a leak is present before the waste gate, the turbo may produce excessive pressure and cause overboost but he does not believe in using the pressure test.
3) He claims that the pressure test will give false results because there is always a leak present in the turbo around the shaft of the impellers, because there is no oil to do the sealing when engine is not running!!! (I find that very hard to believe someone in his position is saying something like this)

Remember, this is the guy that took 3 visits , 3 mass air flow sensors, and finally a completely colapsed air filter to find a busted TBB, and he never used the pressure tester to find it. Soon after, both turbos had to be replaced.

Give me some amunition guys! and thank you in advance.

get a new mechanic!

Call me crazy but have you thought of changing tech's?

I am stuck with those guys
 

Please give me a brake. This is the only dealer for me. The next one is 100 miles away.
I want this guy to apologize. He shows no respect. Audi wont be too impressed to hear my story and realise how much my car cost to them while on warranty. Now at 180,000 km my warranty is over and I want to prove my point and get rid of this a.. H...

I need to have it in writing on Audi tech paper, that when code "overboost", you should do intake pressure test.
Thanks.

Well
 

I can't say for sure where that would be written. Do you have any other fault codes other than the over boost?

Re: A6 2.7t , 2000 with overboost code...
 

we will fight it to the end brother

Re: A6 2.7t , 2000 with overboost code...
 

Sounds like another slight tear in the TBB. By being slight it wont leak under normal load, then with heavy load, the tear opens somewhat and no power. Then when you driving around town nice and easy, everything is fine again. It will end up ripping the boot.
Just a guess.

Dude, I just had that and fixed it by finding the leak. TBB slipped off intake.

Re: Well, well...
 

obviously they did not show me the numbers. I can ask to see them. I will ask to get a print out of the codes. And in the end, don't they have resources at Audi Corp. to help them find problems? What numbers would you like to see?

I read all responses to your post, just go buy a VAG Comm software and empower yourself
 

Theres an awful lot to be learned in that car 3with the right software. It sounds like your a pretty smart guy, so learning how to use Vag wont be hard. theres also a vag forum around here somewhere.


good luck

17965 Positive Pressure Control: Positive Deviation is the overboost code, right? There are a lot
 

of sheisters in the business. I took the car in to be checked out by private company started by ex-factory trained VW techs. It was in pristine condition. Get it back and I am chasing codes and I find out they set my turbos up to fail. They undid the clamp to the intake hose after the MAF leaving the hose partially on without changing the air filter. They reinstalled one DV backwards. Now, I found they reinstalled my TBB half on. All of this was checked prior to being taken in. I have photos and am considering a frivolous small court claim and some local exposure in the newspaper via a news contact. I am telling you this because I am curious if they train you guys on ethics at Tech school. Or, is it just straight forward technical education. Thanks.

Do a search for the AWE pressure tester.
 

You want to pressure test the diverter valves (using a basic vacuum pump), and pressure test the intake as well(with the AWE tester, or one created based on its plans). Surging, as you are describing, is often associated with bad diverter valves. Also check the TBB for tears as others have said.

Don't forget to do a search for "postive deviation" as that is what the code shows up as in the ECU.

Example:

17965 - Charge Pressure Control: Positive Deviation

Another thought is a bad n249 valve; this is the valve that controls the actuation of the dual diverter valves in the intake. I forget what the value is, but you can check to see what the voltage across it is with a multimeter. I tried a search, but couldn't find what I was looking for.

You might hit up the S4 forum if you hit a dead end. Those guys are very helpful, just make sure you have put forth the appropriate effort in searching first : )

Good Luck,

-st

They finally put the pressure tester on...after putting on the pressure!
 

They found a leak in what looks like a F tube in the rear left about 5 inch from the center line. It was a very small leak according to the mechanic. They are ordering the part today. I will have the parts in hand later and will keep you posted. Thanks for your constructive replies to you all!

Infamous F-hose!

I faxed your recommendations to the mechanic
 

Thanks. Very much appreciated. As for the codes, i don't know what they are precicely but this should put them on the track.

just added to my Christmass list from me to meself!
 

Merry Christmass and with all you guys help.

Get a Samco, ECS tuning sells them for cheap. The F will fail again later. Just $.02.

Cool - very common failure.

Re: They finally put the pressure tester on...after putting on the pressure!
 

good
we are almost getting somewhere
good luck

Re: A6 2.7t , 2000 with overboost code...
 

Sure enough it was a leak! F-hose!
No comments about the dealer but you guys were right. thanks to all.