PDubbs20AE

So I just got my car on the road after purchasing it and having to let it sit for a month. Long story. Anyway I have a TCarbon FMIC on the car and made sure everything was nice and tight, start driving and was spiking at 22 psi. It was nice and quick and then all of a sudden I can't boost past 5 psi. I checked around and find that I'm stuck in a limp mode.

So my friend and I check everything, and get to thinking that it has to do with the DV, my Forge Splitter. We tighten down the spring because it is letting boost out very fast. Tighten it a bit, then find that it still won't boost past 5 psi. We reset the ECU by disconnecting the negative from the battery for 5 minutes. Now sometimes it will boost fine, other times I get stuck at 5 psi.

Could it still be the DV? I can't see where a boost leak would be, but maybe that? I did receive a code, P0172 which is too rich but that might be from the way the car is acting. I have also heard that it could be the N75 spiking and sending the car into limp mode. Could it be this? If so what is a fix? Thanks!

SlapTTy

I assume you have it chipped? Did you VAG-Com it?

PDubbs20AE

Yes, chipped by PO, APR 93 software. I have not run a VAG-COM because, a. I don't have one, b. I'm lazy and didn't use the locater, and c. I'm strapped for time right about now, finals and projects, so I can't exactly lose an afternoon or so.

It is at the shop now and I'm having them run a vac test to check for leaks, and also replace my front axles since the boots are ripped open on them. Front axles only though so the damage won't be that bad.

Peter Badore

Try substituting a known good N75 valve. A bad N75 will put the 1.8l turbo engine into "basic mechanical boost control" according to Audi's TT service intro manual .