intermittent boost problem

Peter Schulz pcschulz at
Mon Aug 20 17:01:36 EDT 2007

I would check the distributor position (rotor in respect to the #1 
cylinder TDC position.)
I had a similar issue with boost cutting about 4k rpm with MRC stage II.
(and yes, the 3B distributor can be "close enough to start" but still 
off enough to cause the cut back of boost above 4krpm and again around 5krpm)

You _could_ mark the position of the Distributor body in respect to 
the valve cover, then move it a hair in one direction, then the other 
( this way you don't have to pull the distributor cap..)

Scott Mockry has some instructions and pictures at


At 04:50 PM 8/20/2007 -0400, Brian C. Mills wrote:
>I have been trying to track down a boost problem on my 200 20v sedan for a
>while now.  I am fairly new to this so please excuse any mistakes I make in
>providing the appropriate details.
>I have 146K on the clock with original turbo, manifold, exhaust.
>Stage III+ Chipped ECU from Intended Acceleration
>Samco Silicone Boost Hoses
>TurboXS Bypass valve
>All of these mods were done by the previous owner.
>I have driven a few other 200 20v (both sedan and avant) with similar
>configurations, so I have a point of comparison when I claim to be having
>Boost will cut out and surge back.  For example, in 3rd gear WOT, the stock
>boost gauge will briefly hit 1.8 and cut out completely to 1.0 or less and
>then return only to cut out again.
>The frustrating part is sometimes this won't happen, so I have been told by
>"audi mechanics" in the past that I have no problems.
>The check engine light is on.  If the fault codes are read it may list one
>of the following codes:
>Internal ECU Fault
>Engine Speed Sensor
>I also have a stock ECU, when the stock ECU is in no fault codes are read.
>I have been told that the Internal ECU fault is common on modified ECUs and
>should be ignored, should it?
>I have checked for obvious signs of boost leaks and found none.  Eventually
>took it to a tuner and had it "smoked", they confirmed there are no boost
>leaks in the system.  The tuner put the car on a dyno and found:
>"The car made about 193 hp to the wheels and a 210 lb torque to the wheels.
>However, the boost is being electronically cut at about 5300 rpm."
>Their most recent guess is that something is wrong with the wastegate.  I
>have taken a look over the troubleshooting list at
> but I am hoping
>someone here will be able to narrow the list down a bit.
>Thanks for your time and sorry for the long post.  Please feel free to post
>suggestions off list if you think this topic has been too well covered in
>the past.
>Brian C. Mills
>200q20v mailing list

-Peter Schulz
Chelmsford Ma, USA

1995.5 S6 Avant Emerald/Ecru
1995.5 S6 Avant Silver/Platinum
1991 200 20v Q Avant Titan Grey (for sale)
1991 90 20v Q Red
1991 CQ silver  (eS2 recipient) 

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