Audi S3 boost problem

[woodyS3]

Hi all, Over the last couple of months ive had occasions were ive started my car and its fine and goes like stink, then when i turn the engine off and get back in it say half hour later i have no boost and it drives like a N/A 1.8 engine, this also happens if ive been stationary for some time at traffic lights for example. The turbo sounds as if its working as i can hear the DV working but its very quiet, to get it to boost again i just go through the gears all the way to 6th, pedal hard down and then drop down to 3rd or 4th and this seems to get it back but its annoying me now and i need it fixed. Its got a brand spanking new Forge 008 DV on there so that shouldnt be a problem but what do we think it could be? Faulty n75 valve? Faulty actuator? Boost leak?

This is my first thread so please be gentle, all help would be appreciated.

P.S Its a 2000 reg Audi s3 ABY engine

Thanks

Woody

 

[<tuffty/>]

Welcome to ASN Woody...

First things to do is scan for fault codes and check the engine bay over for obvious split or loose/detatched pipes... check under the inlet manifold as they tend to split there..

Is the car mapped? has you had or under taken any work on the engine recently?

<tuffty/>

 

[s3dave]

Could be a pipe that is cracked, that is opening up at a certain temp and may be very hard to spot, as above see if there are any faults, then a smoke test would be my next port of call, if you cannot see anything split/broken..

 

[woodyS3]

Hiya thanks for replying, I've been on here for some time but thought I'd actually post something tonight. Yeah the car has been remapped but that wasn't long ago and it was doing it before hand but not as much as it is now. I know it could literally be anything but it's not throwing up any fault codes on normal diognostics as I've had that cleared 4 times in the last 2 weeks due to my b@stard haldex controller. Anyway I've seen on other peoples posts that it could be a n75 or a sticky actuator but is there any easy way of finding this out ( please bear in mind although I'm an electrician I have the mechanical know how of a chimp ) also I don't have vagcom to check but if someone can give me guidance, I can forward this to my local garage as they don't usually have a clue what to do on my car and I normal just relay the advice given on here to them.

Also worth mentioning I've disconnected my maf sensor before but this had no change but I did do that when I had no boost and I haven't tried it when I have got full power which is usually on first start up. I'll try it tommorow on first start up and see how she goes but it is a relatively new maf so I hope not but we'll see. I presume that if it's disconnected and it runs like it does when I have "no boost" that could be a likely culprit?

 

[woodyS3]

Ok just been out to disconnect the Maf, started it up and as i expected the esp light came on, went for a drive and i felt slow but still had some turbo boost but obviously not as much as in normal driving conditions. So i think i can rule out the maf because when it comes to a situation where i lose boost it feels as if the turbo has gone on strike and there is no power at all.
I guess it's time to look at the N75 valve, smoke test for possible boost leak and actuator. How easy is a smoke test and is there any test i can do to find out whether the N75 valve and actuator are knackered, im guessing disconnect the N75 valve but i'd be lying if i told you i knew what or where it was.