A4 a-go-go

[Justin Fidler <justin@codeboy.net>]

So my A4 decided to add a little throttle that I didn't intend yesterday
night.  I won't call it UA because I know how to use my brakes, but it
still shouldn't happen..

The car: 1997 A4 1.8tq, with automatic transmission (not tip) and Wett 1.0
bar chip.  The car has about 10,000 miles on it, and the chip was
installed around 8,400 miles.

The situation: I was driving through light traffic in a DC suburb.  I made
a left turn at average speed and approached a red light.  I was
decelerating, and as I was getting closer to the car in front of me, the
rpms started climbing, up to around 2,000-2,500.  I immediately hit the
brake, but not as a panic stop (the car was still moving slowly, which was
ok, because I had room to spare).  Then the transmission "thunked", with
the same sound it makes when it's at a higher-than-1000 rpm and it drops
into gear (so maybe it was in neutral for some reason?  I know the
selector was in drive).  The rpms dropped down to around 1,000, and after
I heard the thunk I stopped the car and put it in park.  The rpms started
climbing again, to around 2,000.  It didn't get there super-fast like if I
was flooring it, but it wasn't just an over-zealous idle.  At this point,
I turned the car off and started it up again, and it seemed to be fine.
The whole incident scared my date a little, as I had been explaining to
her the unintended acceleration hoax a couple hours before :)

I can understand the climbing RPMs while I was in Drive, because the auto
transmission will use engine braking while you're decelerating, so it
could've downshifted.  I guess I can also understand the thunk, as this
happens every once in a while, when I'm at a moderate decelerating speed
and I accelerate (so the thunk can occur).  I don't understand why it
occurred while in Park.

I have a couple clues.  About a week ago, when I would start my car (I
always start with foot on brake, and never push down the accelerator
before/during starting), it would jump to around 2,000 rpm on starting,
then come back down.  Usually it just jumps to about 1,200.  Then, a
couple days ago I refueled and as soon as I left the gas station, the
check engine (MIL) light came on (it's still on).  But this has happened
before, and it's fairly common in OBD-II (north american) cars, according
to some back-posts on A4.org (the emissions stuff is too sensitive).  

So here's my issue.  I'm going to take it into the dealer this week to
check it out, and have them pull the codes.  It seems like an
idle/throttle problem *could* be linked to the ECU chip, in which case
maybe I should put the stock chip back in its socket.  However, I don't
know how the ECU works.  If I pull the chip out, will it erase the
computer's memory of malfunctions?  I assume the MIL light is causing the
error codes to be logged, and maybe pulling the chip breaks a circuit, if
the codes are stored in volatile memory.  Anyone know?  Is it worth it to
put the stock chip back in for the dealer service (it's a bit of a pain
to do)?

In other news, I have completed a rite of passage for D.C. residents.  I
saw Monica Lewinsky yesterday afternoon leaving a restaurant (Mrs.
Brown's, on McPherson Square, near the White House).  It looks like
she's lost some weight.  Now I can go to cocktail parties without feeling
inferior because I didn't have a "Monica story" :)

Thanks,
Justin