A4 1.8T Sport Quattro @1 PSI??? HELP???

[deejay]

I love our A4 but i'm losing my hair FAST since we bought it! It WILL NOT come on boost! We bought the car from an auction and so were unaware of the problem beforehand.

The most i've seen on the gauge is 1 PSI! I can get that to go to around 3 PSI by bypassing the N75 and disconecting the actuator ... I've done all the leak tests, changed the coolant sensor, tried a new MAF on it and had the Snap-on scanner from work plugged into it but nothing obvious came up. Anyone got any ideas?

I'm taking it tomorrow to have it plugged into a Delphi scanner which is supposed to be the best on the market at the moment so we'll see what that says. I think i'm gonna buy an ebay lead and download a copy of VAGCOM so at least i don't have to rely on anyone else to diagnose it. Which lead do i need? Are they all the same?
Cheers,Dean.

 

[macattax]

Search for a guy called alphabid on ebay a lot of ppl including myself have bought leads of him he is reliable and quite cheap.

 

[Blue_Thunder]

By disconnecting the N75 you will only be getting mechanical boost, ie: only as much as possible before the wastegate spring is forced open. On the S4 (with 2x K03's) I think you get up to 5psi mechanical boost. I guess with one turbo, 3psi may be right. If that is the case, your turbo isn't seized.

Just seems strange that you are getting less boost with the N75 plugged in as I didn't think a turbo could produce less boost than the mechanical boost (once spooled up).

I'd suggest getting someone that lives nearby with a registered version of vagcom to take some logs of the specified and actual boost. As odd as it sounds, it doesn't sound your ECU is actually requesting any boost.

 

[deejay]

I've been with it this morning to a local diagnosis specialist that i know has a good reputaition and even HE was baffled by the thing! The only thing obvious was that the intake air temp sensor was saying 37.5 degrees...

 

[PhilR]

have you checked your actuator ?

Mine failled before and i was seeing similar boost levels to yourself, the spring was snapped inside it allowing the wastegate to e blown wide open .

Antoher common problem is that the wastegate valve has a pin on it to stop it spinning on the arm, this pin tends to snap and the valve starts spinning when the wastegate is open it eventually drops off and goes into the exhaust system