[200q20v] Low Boost Puzzle - Help needed

[Phil Rose]

Steve,
I'm not sure about codes for a "defective" TP, but have you considered a
misadjusted TP as a possible cause of the low boost? Also, be really
certain about the condition of hoses--they can sometimes be very difficult
to spot. For example the narrow vac/pressure hose that controls the TBV
(bypass, or cutoff valve). It is very vulnerable (but hard to examine)
running under the heatshield, and it invariably becomes toasted sometime
between 50 and 100K. Then there's the possibility of a defective TBV,
itself. Another symptom of TBV problem would be stalling when coming off
boost to a quick stop.

BTW, welcome back to the '91 20V200q "club". But won't you be missing the
sound of rear Bose speakers in your avant? :-)

Phil

At 10:30 AM -0500 12/3/00, Steve Bednarski wrote:
>I should be receiving the VAG-COM software soon from Uwe Ross at Ross-Tech
>and was encouraged by preliminary testing on my 1991 200Q Avant.  I will
>post more details after I receive the software
>
>I would like to hone in on the following:  My boost pressure on the car
>reaches a maximum of 1.5 Bar on the gauge.  I believe that the gauge is
>correct as the car does not feel as fast as the prior 1991 I have owned.  It
>is barely faster than my 1990 10V 200Q.
>
>Here are some key additional details:
>
>1. All output checks work and the WGFV clicks during this test.
>2. A fault code for the speed sensor is the only one that appears.
>3. All hoses seem to be in fine shape with no evidence of cracking on this
>low mileage (59,000 mi.) car
>4. New plugs, oxygen sensor, and distributor cap have been installed.  The
>distributor rotor was fine and not replaced.
>5. Highway fuel mileage is 24mpg at 65mph (which seems a little low)
>6. Car runs and idles smoothly.
>
>Where should I look in order of priority for my low boost problem?  Can I
>still have a defective throttle potentiometer, for example, but not have it
>show up in the fault codes?
>
>Any help would be appreciated.
>
>Steve B.
>
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*  Phil & Judy Rose           Rochester, NY  *
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