It's SOOO frustrating! I've boost tested (no leaks), Replaced N75, Checked all lines and hoses. Replaced DVs with new 710Ns from ECS tuning (which I can hear honking sometimes when I have the full 1.1 bar)..

No codes on durametric.. usually when it's cold, (been sitting a few days) I will have the full boost for about 5-10 miles... then back to 0.5bar.. and trust me when its hitting at its 1.1.. HOLY CRAP its awesome, but doesn't last. Sometimes If its a 100 mile drive, it will go in and out with the full boost.

It's either 0.5 or 1.1.. never like .8 or .3 bar.. half or full pretty much.

No stuttering, misfires, rough running. Driven car about 1500 miles now since I got it, hasn't even used 1 bar of oil on the digital gauge!

Only thing left to check is wastegates with a mityvac.. If I manually move wastegates by hand, its tough but they move (don't know whats normal or not)

I feel like if I give it to a shop, they will do the same tests I did and beat the **** out of my car trying to figure the damn thing out.. so don't want to do that. Unless its someone you guys trust here in Indiana.

Going to check catalytic converters to see if they are loose next week (highly doubtful)

Could it be a bad turbo???

03 turbo, k16s, giac flash, gemballa exhaust

 

diverter valves checked? maybe wastegates going hard

 

Ughh... I feel your pain! My car has been having the same issues - one day its .4bar the next day its 1.0bar.

Can you detail your boost leak testing procedures? What did you plug up? It held up to 20psi flawlessly?

I'll try to detail my own experience, maybe it will help?

In my case, when I plug the turbo outlet hoses and try to pressurize, it wont even get up to 4psi and quickly all leaks out. So I know I have a leak.

Next, I plugged up the exit of the Y-pipe where it goes on to the throttle body. I also took off the hose and plugged on top of the Y-pipe, near the pressure sensor and I took off the small hose going to the N-75 and plugged. I tried to isolate the tract of turbo outlet, intercoolers, Y-pipe and DV's. Basically want to take anything after the throttle body out of the equation. Now it quickly pumped up to about 8-10 psi, when one of the DV's would open up everytime and let the boost out. That's one problem but not the whole enchilada. I replaced both of them. I should now be at the point where the turbo exits up to the throttle body are good and tight. But with the Y-pipe attached to the throttle body, I still can't get over 4psi. I've sprayed a whole bunch of soapy water, looking for leaks. Haven't found any. I know my issue must be somewhere after the throttle body, and it could have something to do with the various rubber hoses coming off of it.

I *think* my problem is the infamous check valve. It is on a hose that comes off of the intake manifold, after the throttle body. The hose is supposed to allow flow into the intake manifold (I think for fuel vapors) but the check valve is there so pressure can't get back out. If the check valve is bad, you will have boost going right back out of the intake manifold - and it wouldn't be a leak that you would see with soap and water or smoke, since nothing actually leaks out into the atmosphere. \

So as for me, that is my next thing to check. I believe you have to lower the engine a couple inches to reach the cehck valve.

Check out this thread, this guy had a bad check valve.

https://www.6speedonline.com/forums/...-pressure.html

Best of luck, like I said I feel your pain!

 

When I pressure tested I blocked off the intake and one side of the turbo, and pushed air in thru the other turbo. Pressure held well.

 

how old is the tune? did you buy it with the car?
disconnect the maf and run it like that....

 

The tune came with car, I have an OBD loader to put it back to stock or run the pump tune.

I will try the MAF disconnect..

I have attached the log of when it was acting up.

 

What kind of exhaust are you running?

 

Gemballa, came with the car, probably installed in 03 I would assume.

 

Sorry. I missed in your first post that you already checked the cats & mufflers for blockage issues.

Sounds like a real gremlin. I wish I had something else for you to check, but I don't.

 

Actually I still have to take the exhaust down and check for blockages, so hopefully that is the problem!

 

I had a similar issue which was crazy but i had a bad clutch switch which was signalling my 2 step mid acceleration. Try replacing the coutch switch. I never through a code

 

This is very frustrating problem, I had it for a year because the tech I was using was a lazy POS. Changed many parts only to have it continue. Finally took it to a real diagnostician who spent the time. He found one of the CATS had come loose and was blocking the exhaust. Never got a CEL, or heard any rattling, or any other telltale signs. Higher boost pressures can unseat these older exhaust CATS. Don't change any more parts until you take off the mufflers and inspect. Good luck.

 

This is why I love cat-less exhausts. Good luck!

 

My car had a damaged ECU and it had to be rebuilt. Car running EVOMS DV's, Speedtech exhaust, etc. so the normal culprits were checked.