Hey guys a new issue has sprung up and I'm searching for solutions. When on hard accel and wide open throttle... the boost goes up to 21psi (as it should) and then will suddenly fall to about 10, rise to 15, fall to 10 rise to 15 again in the span of about 1.5 - 2.0 seconds.

I saw a youtube video showing a boost gauge acting in precisely the same fashion, and that user later commented that his TPS was not programmed for his chip. I have no idea what software is in this car, as it was installed by the original owner.

I was also thinking maybe the previous owner had the wrong spring in the Forge DV valve...or possibly the DV valve needed cleaning....

Any suggestions?

 

If it continuously does 10-15-10-15, it is probably your N75.

 

You were right. Since I originally posted about this issue... when the issue presented itself, it got so bad that instead of bouncing inbetween 15-10psi... as soon as it got above 10psi it would flutter violently and emit a loud buffeting sound like a muffled machine gun.... it got really bad.

So, earlier today in the Advance Auto Parts parking lot, I pulled apart the whole intake, ginseng root and all appertaining parts... cleaned out and regreased my Forge DV valve, cleaned out the bypass valve (it was gunked), degreased all the plumbing and took the opportunity to dispose of all the "onetime" clamps still left and replaced everything with nice new hose clampss.

The N75 valve housing was highly oxidized and the elec connection was very dirty. I blew into the intake side and it was flapping. I did my best to clean it out and I soaked the connection with Elect Contact cleaner, knocked out some debris that was inside the "T" chamber and reconnected. Zero issues now after 20 miles. I'm still going to replace it, but at this point I think I'm going to replace the whole inlet pipe.

 

So Since I first responded back on this.... after I cleaned everything out it ran fine for a few miles... then the problem came back and grew progressively worse.

As of last week it started getting so bad that as soon as it would get above 8PSI it would flutter violently and loose pressure. It almost sounds like it's "farting" and will not get above 10PSI.

It's really violent and upsetting when it happens. I replaced the N75 valve with the VW/AUDI stock part. No change. Removed and thoroughly tested the FORGE diverter valve.....its fine. Checked vacuum... no leaks. If I let this happen for a few seconds, I will get CEL and codes related to exhaust O2 sensors. Just for the sake of getting more data, I DISCONNECTED the wastegate actuator from the vacuum system to see what happens. PROBLEM REMAINS even after disconnectiion...so it can't be the wastegate SO WHAT THE HELL COULD IT BE?

I have checked everything. I have no idea what to do. Again: the boost builds normally... perhaps even slightly faster than usual... hits ~10PSI (normally spools to about 18PSI and tops at 21PSI near redline) and INSTANTLY begins to violently flutter, making a buffeting or fluttering sound, and boost will not get above 10PSI, just shudders between 6-10.

Does anyone have any further suggestions? If there's anyone who can dedicate some time to helping me with this I am only more than happy to paypal a few dollars....

 

It's getting to lean and throwing it into a safe mode until boost drops again and normal operation continues
These are just my thoughts

Try driving around not under boost and see what it does

I'd check the O2 s
And anything fuel related like maybefuel pressure regulator