I get negative pressure off boost. When I accelarate, boost gauge goes to 0 and stays there, until I stop accelarating, and then I get negative pressure again. I can 'feel' that there is no boost.
I've checked intercooler piping (r and r'ed it), still no good. There is NO smoke at all. What should I check for?
Thanks.

 

I would check all of the fitting coming from your turbo all the way to the throtle body.

 

yank off the TID and see if your turbo still spins...

assuming it does.. check the pressure sensor vacuum line, because if it's partially come off the pressure sensor will act like that.

Check your intercooler hoses, when they blow they work fine under vacuum but then leak all of your boost...

 

Don't I have to take off the Upper intake manifold to get to the turbo? I'm just trying to do a quick check, for easy accessible items.

 

I got a turbo for an s4 if yours is bad make me an offer

 

Okay, we took off the TID and found 2 things.
1) The turbo seems to spin ok. There is a little play, side to side, but not much.
2) The TID had a a 1 inch crack along the side. We sealed that up (you'll have to ask Amur about the details of that), but that did not help. In fact, the boost gauge now won't even go to 0 (about half way to 0).
There is still a loud 'howling' sound coming from the engine area (I forgot to mention that before), and it seems to coincide with the car trying to get into boost.
I'm confused.

 

Hate to say it but when my car did that, my turbo was toast. It would go right to 0 and NEVER go above it no matter what. Just make sure all your vac lines are on and there are no leaks first.

 

1. check TID
2. check to make sure the wastegate arm is still connected to the wastegate rod. The c-clip that holds the rod onto the wastegate swing valve tends to fall off sometimes and then the wastegate is just swinging around. I don't think it's the c-clip as you still get boost, just it's like trying to spool a t72, no boost until like 6k.
3. check shaft play of turbo, sounds like you might need a rebuild or new turbo.

 

The stock gauge, yes. But it wont make the car feel slower.