[s-cars] Thank you Bob Pastore! (the sequel), and my annoying boost problem

[Bruce Mendel]

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Once again, Bob has offered his time, ideas, and wrenching skills to help m=
e try to solve a tough problem with my car. Oh, and he let me use parts off=
 his car to try on mine, too!  :) Not only that, but when we dropped a part=
 into the pan while HE WAS TRYING TO FIX MY CAR, and I had a meeting in 1/2=
 hour and could not get dirty, HE GOT FILTHY GETTING THE PART BACK! Sorry, =
Bob, I owe you a shirt! Seriously.

What did he do to deserve this? Bob has the misfortune of living within dri=
ving distance of me, hence my haunting him now and again. Plus he helped ho=
ok me up with some cool parts too. So I hereby nominate Bob for Audi Sainth=
ood for his true "no obligation" offers of help. I met Bob when he needed a=
 spark plug at a track event, so at least I have returned one favor, thank =
god.

The problem unfortunately, remains. Description is as follows:

During track event, car was running fine and then I got a check engine ligh=
t at full throttle, full boost in 4th gear. Car did not buck or stumble, bu=
t boost was dialed back to 8-9 lbs (spring pressure I believe), then if I k=
ept my foot in it for a few seconds, boost would "pop" back up to normal. C=
heck engine light that day said "hi/lo fuel mixture problem" or something a=
long those lines. It initially only happened at high RPM, and especially ju=
st after a shift when going back to full throttle.

There is no misfire, stumbling, smoke, and the car does start off developin=
g full boost before it's cut back, so clearly nothing major is broken or le=
aking, as I would think the car would not run well to begin with. It just s=
eems like the ECU gets a signal it does not like, cuts back boost to minimu=
m, then think all is OK, lets boost go back up again, and then repeats proc=
ess.

Since then, the problem has become more consistent, happening nearly every =
time the car gets up in the RPM band at full throttle. It happens more ofte=
n, and at less aggressive throttle and boost settings, on the track. I can =
get it to do it on the street, but it takes more effort. Check engine light=
s thrown since that first day have also included "cam position sensor inter=
mittent to B+".

So far, we've swapped ECU software, entire ECU, all fuel injectors, BPV, MA=
F, WGFV, and a new cam position sensor was installed, prior to this problem=
, about eight weeks ago.

Any ideas? Thanks all, I love this list!

Bruce
'93 S4, still limping
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