Boost problem. Already done a leak test

[cdc]

I have been getting a CEL code for P1557 Charge Pressure Control: Positive Deviation but it has not been activating the CEL light on the Cluster.

I have used AWE's instructions on how to do a boost leak test as I have been hearing what sounds like a rushing of air escaping from somewhere when I accelerate from a stop hard, which I thought would be a boost leak. But its not the test did not show any leaks.

AWE's instructions says it will only find leaks before the throttle body not after. Is there anything I can do to check for leaks after the throttle body?

I have also read it could be a problem with the N75 valve. Is there anything I can do to check it? But I don't have a VAG to do logs.

Any help would be much appreciated.

[mholme]

I have been getting a CEL code for P1557 Charge Pressure Control: Positive Deviation but it has not been activating the CEL light on the Cluster.

I have used AWE's instructions on how to do a boost leak test as I have been hearing what sounds like a rushing of air escaping from somewhere when I accelerate from a stop hard, which I thought would be a boost leak. But its not the test did not show any leaks.

AWE's instructions says it will only find leaks before the throttle body not after. Is there anything I can do to check for leaks after the throttle body?

I have also read it could be a problem with the N75 valve. Is there anything I can do to check it? But I don't have a VAG do logs.

Any help would be much appreciated.

Boost leak is highly suspected. What mods on your car? Chipped? Boost gauge?

[cdc]

Car is completely stock and unfortunately don't have a boost gauge.

Also I forgot to add my drivers side valve cover gasket is leaking, i'm not sure if that would affect anything with boost.

[cdc]

anyone?

[Matt@JHM]

Well, I am pretty sure positive deviation means the car is boosting more than expected. If that's correct then search for overboosting. It is usually caused by a bad n75 valve or in more extreme cases, a torn vacuum line to the waste gate.

[S4-ORCE]

Check your Diverter/By Pass Valves, also might be your N75. Also what psi did you pressure test to? If you have a stock throttle body boot, def. check and re check that.

[The_Jerbel]

Try a known good N75 valve and also pressure test the hoses going to the N75 (the one on the driver's side of the valve).

[cdc]

Ok thanks guys. I pressure tested to 15 psi and could not hear any leaks, i will try and pressure test the N75 lines over the weekend. But if they hold pressure it looks like the N75 valve is shot.

Should i test all the n75 lines or just the drivers side?

[The_Jerbel]

Just the driver's side...

[cdc]

I pressure tested the drivers side hose today and it seems to hold pressure, so it looks like I will have to replace the N75 valve.

Does anyone know where the cheapest place is to get one?

[Mantis]

Check with Avalon in Denver, ask for Brian. def would suspect that you are overboosting due to bad N75. A boost gauge is a fantastic investment, if you dont want to clutter the interior with the gauge consider EFU 4U, using your drivers information center to show you vital car info like boost.

[The_Jerbel]

I can get you one for a good price, PM me if you want.

[Mantis]

sorry Jordan, didn't thinkk to recommend you

The Jerbel can get you one quick and cheap, lol

[eliTTe]

I seem to be having similar problems, but no codes yet. when I first drive the car and boost it, it makes that rushing air sound with a little whine to it. and boosts to 15psi instead of 19psi. then I shift and its in limp mode. the sound is comming from the drivers side of the motor. no boost leaks

[The_Jerbel]

Test your DV's.

[Audi S4 Turbo]

I had that problem when I was over boosting. I have a mbc and I turned it down and it ran much better.