Auto ECU's use the sensors to control fuel according to the voltage
supplied by them. Most sensors output 1 to 5 volts. More volts is
more fuel. The new drive by wire open the throttle according to the
throttle position sensor.
That is also trimmed by the traction and ESC controls built into the
software.
 The O2 sensors are different in that they only operate on .1 to .9
volts.
They generate this voltage in response to the O2 in the exhaust. The
ECM is trying to maintain an A/F ratio of 14.7 to 1. This coincides
with a voltage of 0.5. Diagnostics have an output of cross counts
which is the number of times per second this voltage crosses the
0.5V's. A high number (cross counts) is desireable for emission
controls. As with other sensors, more fuel translates to higher
voltage. The ECU then shortens the pulse width, (gives less fuel) to
respond to the excess fuel in the exhaust. An O2 sensor that has low
cross counts is due to be replaced. Fuel economy will likely be
improved. O2 sensors SHOULD not have anything to do with the
throttle position stepper motor. As with any man made device,
anything can and probably will go wrong.
 A few years ago, Audi had a lot of trouble with the UNINTENDED
ACCELERATION PHENOMENOM. One of the car magazines did some reasrch
and found the fault to be small close pedals that low time (new
owners) mistook the gas pedal for the brake pedal. In each incident
the owners were positive they were stepping on the brake. The
magazine testers were the same as the new owners that had their car
take off. ALL CARS ARE DESIGNED WITH BRAKES THAT CAN HOLD THE CAR
BACK.
Modified vehicles MAY be an exception.
 In the expert witness case, the driver could not have had their
foot on the brake pedal firmly when they put the vehicle in reverse.
If it had been so the vehicle may have moved slightly, but not
enough to kill anyone. IMHO.

Dale Davies


--
Dale
 I can tell you from experience that the Audi problem was real.  I
don't know what the problem was but it wasn't small close peddles.
I had an Audi and experienced an uncommanded acceleration.  Here is
what happened.  I turned a corner on a city street and started to
accelerate and the car throttle body went "Wide OPEN"  the RPM went
to about 6K.  I stood on the brakes and it was still accelerating
and about to hit the car in front of me so I kicked the transmission
into neutral and without a load the engine RPMs pegged for a split
second and then dropped back down to idle.  I parked the car on the
side of the road and called the local Audi dealer... Keep in mind it
was "Not" under warrantee. They immediately picked it up, gave me a
free rental and fixed it for free.  Oh, this was the 4000S model and
not the 5000 model car that was suppose to have the "Problem".  I
don't know what was wrong with it but I do know it wasn't "peddles"

Mike C.



Not necessarily calling bs, but I don't get it.  There's not a car
made that can accelerate as fast as it can decelerate.  That implies
that the brakes are able dissipate more energy than the engine can
deliver.  I believe the engine might have gone to WOT, but I have a
tough time understanding how the brakes wouldn't be capable of still
hauling the car to a stop.  One factor is that if the engine is at WOT
and you pump the brakes, the booster would quickly lose vacuum and so
you'd be without the brake assist. It might take a heavy foot to get
much braking effort, but the same braking power would be available.
And, I can imagine that it would be surprising as well..


Matt-

I have not tried it Matt but one can "fade" the brakes.
This is when the pad material gets so hot the coef. of friction goes
way down. It is a runaway situation. The longer you
hold the pedal down with full power the worse the brakes
get. Also brakes boosters work on vacuum. WOT vacuum is near
atmospheric pressure.

Brake fade is very common in road racing. One of the
first things you need to do to convert a car to a road race
car is upgrade the brakes.

Paul Lamar