re. low boost question

Ben Swann benswann at
Sun Apr 16 22:47:41 EDT 2006

When boost is at or near atmopheric pressure as is yours, that generally
indicates a leak under pressure.  I'd suggest checking the Michelin man
hose.  Remove to inspect.  They often develop a smal slit that occurs and is
hidden under one of the rings.  It is often not found on initial inspection.
The slit tends to open up on boost, but seal somewhat better under vacuum,
so the car doesn't die and the O2 sensor compensates for a little extra air.


Unless the bypass valve is leaking to the outside or blown open or a hose is
coming off, it is not likely the culprit. When one is not plumbed, the boost
tends to level out much higher - like 1.6.  If the hose were to come off the
BPV, then you'ld be stalling and not restarting.



benswann at

83 urq, /[][] =oooo= [][]\ alpine and Inga

'90 Coupe Quattro (==\ oooo /==) ES2 Conversion

91 200qa20v, [ =!\=oooo=/!= ] avant and sedan

[Date: Sat, 15 Apr 2006 11:37:15 -0500

From: "Brian Larson" <brian.erin at>

Subject: low boost question

To: "200q20V mailing list" <200q20v at>


MY 200q20v starts and runs well, but has low boost.


1.0 or 1.1 bar usually, no engine codes (scanned with vag com), new mfts,
new plugs, cap/rotor.


I am planning to check bypass valve function (and that it is installed in
the correct orientation) next.


Any other likely suspects here?  Intake leaks, etc?




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