chadprosser_

I have a 2001 tt 225, the car always ran fine and never gave me a problem. I got my car tuned by a friend of mine who is very respectable in tuning vw and audis. the car ran great after this and I noticed lots of power gains. about 2 days after I had a major loss in power. was only pushing 5 pounds of boost. got new plugs and coils, new CTS, swapped my n75 valve with my friends ( did nothing) bought a new map sensor and the problem still stands. the only codes I get now are po106 and po238 which both are about the map sensor. I did a boost leak test multiple times and found nothing. I'm ready to give up with this car, PLEASE Let me know what you guys think

Mister Bally

I'd say it's a simple problem like a loos/cracked hose or wire broken. Standard automotive troubles leshooting techniques apply. Or, take it to a repair facility you can trust.

chadprosser_

I did a boost leak test and couldn't find anything, it idles around 20 on a boost gauge

lyleswk

Bally, would a bad diverter behave that way?

Mister Bally

I can't give an accurate answer on that one. Let's wait for Ballykid to chime in....

ballykid

Just to clarify, it idles at 20 psi of boost and when you drive it it only goes to 5psi???

Definitely check you're MAF sensor, sometimes they can either get dirty or covered in oil. Maf failure can cause this 5psi limp mode that you are experiencing. It can also be the DV. My 03 TT is tuned to run 22psi of boost and it was highly recommended to have the DV replaced as the stock ones cannot hold such a high boost rating as they are made of plastic. I have been very lucky as I haven't changed mine yet and I've had the tune for over a year now.
Anyways the DV can stick or else blow themselves to bits causing the pressure sensor in the main vacuum line to think there is an issue and will kick the ecu over into a limp mode.

Mister Bally

Thank you for post Ballykid. The MK1 thread anxiously awaits your future thread discussing (and showing) other engine parts that can "blow to bits" and the road to a complete recovery.

chadprosser_

no it idles at vacuum, I have the the forge 007 diverter valve and checked it. everything is fine on that. I'm starting to think its the ecu itself. I can't find boost leaks and I cleaned my maf many times. I appreciate the feedback though

chadprosser_

I bought a manual boost controller I'm gonna see if that fixes the problem

hahnmgh63

I also get a soft protection mode occasionally to 5psi. When I shut it off and restart I'm back to full boost. Have Revo, 42DD downpipe, VTDA, Blueflame. I'm convinced it's the Revo, changed out a lot of things and it never throws a code? I'm getting read for the F23 Frankenturbo, probably with their manifold so we'll see, might even do another tune. My K04 let go. shaft moves in/out, not a lot of lateral play? A few Youtube videos of K04's doing the same thing. Always used good oil and it only has 98K.