Odd problem with boost.
AudiWorld Member
Joined: May 2007
Posts: 217
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Mines doing something simular...
i only notice it when the engine is cold and only when accelerating very moderately. its very minor, with quick pulses in the power, as soon as i open up the throttle it goes away. i don't even think that anyone riding shotgun would notice it unless i pointed it out. I am still finishing up the 80k service and to be honest i was hoping that it will go away with new spark plugs.
AudiWorld Super User
Joined: Mar 2002
Posts: 2,082
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A new N75 helped mine, but boost leaks were the real culprit
a total of three in the tubing under the intake manifold. The black rubber hoses that attach to the nipples under the intake, and to the PCV valve, crack over time. The hoses are there to distribute vacuum to various systems, but they're also subject to 100% of the boost. They'll leak under boost pressure, setting up the surging condition you described.
If you've had the intake manifold off, retorque it too, a couple of times. New gaskets compress and the fasteners are then loose. Another solid vacuum/boost leak.
None of this presented codes of any kind on my car, just the driveability problem you described... Pressure testing with soapy water found one of the leaks. Repeated testing never revealed the other two. You have to take it apart and look it over very carefully. Replace any hose/connector/check valve that looks suspicious, has visable cracks/splits, or leaks under testing.
Good Luck!!
If you've had the intake manifold off, retorque it too, a couple of times. New gaskets compress and the fasteners are then loose. Another solid vacuum/boost leak.
None of this presented codes of any kind on my car, just the driveability problem you described... Pressure testing with soapy water found one of the leaks. Repeated testing never revealed the other two. You have to take it apart and look it over very carefully. Replace any hose/connector/check valve that looks suspicious, has visable cracks/splits, or leaks under testing.
Good Luck!!
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