Overboost....

[Pysslan]

Hi all

I have a problem with my A2 1,4Tdi. My VAG-COM says "Max pressure exceeded" or something like that and the engine goes into limp-mode.

I believe it is the N75 that's malfunctioning. Does anybody know where the N75 is located and do you have any opinion on my thoughts?

By the way, when I restart the engine it works O.K. for a while then you go into limp-mode again and so on.....

Regards

Leffe

[Skipton01]

Please post a full report from a VAG scan and I'll be able to help you better.

Cheers,

Mike

[spike]

Hi Leffe
Something similar happened to a club member whose car had been performance chipped. He thought it was a problem with the conversion but it turned out to be a vacuum pipe which had come off the turbo - see link
http://www.a2oc.net/forum/showthread.php?t=6003&highlight=superchips

Cheers Spike

[brads]

Hi Leffe,
I had a similar sounding problem with my TDI, where it lost power and shut down to limp mode.The next time i drove it, it seemed ok but then lost power again.This problem turned out to be a split inter cooler, which was replaced along with a new sensor.Also when the connection to the radiator was disturbed (was a bit corroded/furred up), the radiator started with a slight leak.So had to have this replaced at the same time.
Hopefully yours hasn't this problem, but the symptoms sound familiar.
There is a thread on the forum somewhere regarding the inter cooler and this problem.
Anyway hope you get yours sorted, Brads.

[Skipton01]

I'd suspect the loose pipe first, then the intercooler. If it's the former, then it should be easily and cheaply fixed, if the latter, it could cost £250 in parts plus labour.

You could always take advantage of the situation and upgrade the intercooler instead of replacing it - it'll give you more power to boot!

Cheers,

Mike

[brads]

I'd suspect the loose pipe first, then the intercooler. If it's the former, then it should be easily and cheaply fixed, if the latter, it could cost £250 in parts plus labour.

You could always take advantage of the situation and upgrade the intercooler instead of replacing it - it'll give you more power to boot!

Cheers,

Mike

Hi Mike,
Wish that i'd known that when i replaced my inter cooler.What sort of power gains would an upgrade of given me?
What mods are you thinking of next for passing that TT at the next ADI?
Cheers Brads.

[Skipton01]

I'm looking (again!) at gearing mods, bigger intercooler or induction-type work and just possibbly a turbo mod. Don't know though until Allard get back to me.

An intercooler can give another 20PS or so in the right application, but in the A2, I'd say 10 or so.

Cheers,

Mike

[Pysslan]

Sorry for the delay but I have been a little ill and besides, the problem has not occured for a while. But now it's back again.

The fault code is: 17965/P1557/005463 - Charge Pressure Control: Positive Deviation
Possible Symptoms
Reduced power output
Limp mode
Possible Causes
Boost Pressure too High
Hoses/Pipes incorrect connected, disconnected, blocked or leaking
Charger Pressure Control defective
VNT (variable nozzle turbo): nozzles stuck
Solenoid Valve for Boost Pressure Control (N75) defective
Possible Solutions
Check Hoses/Pipes to/between Components
Check Solenoid Valve for Boost Pressure Control (N75)
Check / Clean / Replace Charge Pressure Control
Check / Clean mechanism for variable nozzles

Retrieved from "http://wiki.ross-tech.com/index.php/17965/P1557/005463"

I was logging boost pressure on the way to my work today but the car worked perfectly so I had no help of that. Well, I had a maxpressure (peak) of 2,5 bar (overboost 1,5 bar) at about 2300 rpm and that is pretty high.

The car is chipped (I have 4 AUDI:s, all with turbo and all are chipped :) ) so the pressure should probably be a little bit higher than original but I suspect that it shouldn't be that high.

Any suggestions where to start?

Regards

Leffe

[AudiA2Belgium]

Hi Leffe,
I had a similar sounding problem with my TDI, where it lost power and shut down to limp mode.The next time i drove it, it seemed ok but then lost power again.This problem turned out to be a split inter cooler, which was replaced along with a new sensor.Also when the connection to the radiator was disturbed (was a bit corroded/furred up), the radiator started with a slight leak.So had to have this replaced at the same time.
Hopefully yours hasn't this problem, but the symptoms sound familiar.
There is a thread on the forum somewhere regarding the inter cooler and this problem.
Anyway hope you get yours sorted, Brads.

been there, done that
same problem, the mechanic told me that the cause of my leaking intercooler is that my A2 lays too low +-6 cm(+-2 inches) and i had a bump. repairing is due on the 5th of novembre
greets Sam