Need some help. Trying to diagnose why I cannot boost more than .4 bar. Have a 2005 Turbo S with 17k miles, FVD Exhaust, 100 cell cats, FVD Headers, EVOMS DV and FVD Flash. I am don't drive the car too much maybe 3000 miles a year (hoping to get this number much higher once I resolve this).


Here is what has been eliminated:

No codes apparent (checked with Durametric and PIWIS)
No Boost Leak, smoke and pressure tested no leaks anywhere
DVs hold vacuum properly
Stock Wastegates open at close properly

After eliminating the above we thought it might be that I had some bad fuel in the car and might be detecting some knocking. So I ran the tank to completely empty and put in some fresh 93. Immediately upon driving, the car was back to boosting .8 to 1 bar (have an FVD flash). Great we thought so we call it a night.

Did not drive the next day, but I hopped in the car tonight and its back to boosting .4 bar.

Any ideas??????


Possible Culprits:
-Bad Maf Sensor
-Bad Knock Sensor
-Bad ECU Flash
-Maybe a fuel pump starting to fail?


What do you guys think? Any suggestions on how to diagnose?

Help would be MUCH appreciated!!!

 

Try a drive links test with the PIWIS. Check the vacuum solinoid that controls the wastegates, its the one clipped on the Y pipe leading into the throttle body on the passenger side.

Same situation happend to a customer car, it seems the stock wastegate springs are set for about .4-.5 bar, the vacuum solinoid bleeds off the boost pressure going to the wastegate actuators until it reaches the pre-determined boost level.

I'm racking my brain trying to remember the name of that solinoid in the drive links section of the PIWIS.....dang.