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Boost leak in turbo area

Ever since replacing the FIAV gasket, ISC, and ECU (yes thay were all related /ubbthreads/images/graemlins/frown.gif), I've had idle surge. After boost leak testing, I found a leak at the throttle body shaft seals, and near the turbo. I replaced those with WORKS seals, and fixed it. I also cleaned the TB blade of deposits by removing it. It's shiny clean /ubbthreads/images/graemlins/smile.gif. A friend hosed it down with brake cleaner and scrubbed it, hence the seal failure. Dang friends. Anyway, after doing the seals, the idle is around 3000 RPM.

I re-adjusted the TPS as per VFAQ, and set it within spec. The resistance curve was smooth. I then attempted to set the BISS as per the VFAQ. Even with the proper pins grounded and the screw turned all the way down, I still have idle above 2000 RPM. I am guessing that there is still a large leak somewheres along the intake tract, so I hook up the boost leak tester again. Pressure drops quickly, about 1 PSI every 2 seconds. The leak from the turbo area remains. Spraying it down as best I can with soap water, I can't find the leak.

When I took the accordion hose off, I saw engine oil pooled in the turbo inlet. The PCV system is still installed. Bad shaft seals perhaps, or just the PCV? Could a bad shaft seal be allowing air into the oiling system and be the source of this latest boost leak? I would think it wouldn't be enough to cause such a large idle increase, but I really don't know. I don't hear any other leaks from the intake tract, but it's possible the large leak is making them difficult to hear.

Edit - I'd like to add that the compressor shaft has no side to side or in and out play that I can discern. Just stick your fingers in an wiggle it right? /ubbthreads/images/graemlins/smirk.gif
Last edited by a moderator:


Well-known member
Jun 13, 2004
Lexington, KY
A huge leak like your suspecting will be pretty evident. Does it sound like a huge leak?

My feeling is there's something else going on. Have you put a logger on the car to see what the ECU is actually seeing and doing?


Well-known member
Jun 22, 2005
b'ham, mi
Back of the compressor housing. It's been very common for me. Sucks because the fix is to pull the turbo and remove the compressor housing. Unless you want to just gob some jbweld/RTV on the back of the housing, but good luck with that route...


Well-known member
May 24, 2005
Orlando, FL
Pretty much what Beaner said. My fp3065 leaked at the compressor housing BAD. Took it off and rtv'ed it and all is good. Just sucks cause I wasted money dyno'ing the car and it made sheet numbers.

Spray soapy water around the seal of the compressor housing to the rest of the turbo. See what happens. Don't even post till you do this!
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