This is difficult to describe, and I haven't found anything else on the boards relating to my potential issue, so here goes:

I've had my 2000 S4 for about a month now. Twice I've encountered an intense feeling like i've hit a large "bump", or even feels like I've been hit slightly from behind. But neither of those things happened - I'm positive. The car is chipped, and both times it was turned on. After the first occassion, I noticed that the next time i jumped on the accelerator it didn't seem quite as robust - so I was thinking something was wrong with my turbos... but after a few different tries, the car seemed pretty fast again. Again, I've only had the car for a month and most of my driving has been pretty moderate and distance driving.... not spirited or fast paced, so sometimes I think I forget what its supposed to "feel" like. I also noticed in the manual that the computer is supposed to adjust to your type of driving, and so I figured that the perceived lag was due to an adjustment in my mild driving and that it adjusted itself again when I started driving a bit more aggressive. SO - I chalked the first "bump" up to pure coincidence.

This morning in slow Chicago traffic, I felt it again at about 40mph. I hit nothing (potholes, etc) and nothing hit me. I haven't had a chance to test the speed or quickness of the car again, and maybe my correlation is totally off...but I'm trying to describe everything I can remember.

Has anyone else experienced this oddity, and if so, any idea what it is from?
thanks --- hope the post isnt' too confusing.

 

So what chip u running?

 

Tiptronic .... ??
It could be the downshifting jerk. And yes, the downshift jerk literally feels like someone hit ya from the back or something.
You can try replacing the mounts.

 

It has the APR chip... I don't know much about these things... previous owner put it in.

It does have tiptronic, and the previous owner said in heavy traffic he would manually shift to avoid the hard downshifts... I guess I never thought it would possibly be THAT hard. So, do they only do the hard downshifts occassionally, or is this something I should feel on regular basis?
How expensive / complicated to change mounts?

 

Tranny mounts are the easiest.
But if it is really a downshift jerk. Mounts may or may not help.

And yes, I've seen cars start jerking randomly, especially when they are warmed up.
Its more related to your Transmission Chip.

You can eliminate the reasons one by one.
Tranny Mounts, Engine Mounts, Snub Mount etc.
Also try replacing your tranny chip with one of your friend's if possible, and test drive it for a few days.

Try searching Audiworld.com, with keyword "Downshift jerk". You will find a gazillion posts, and possible solutions.

Some also reported getting rid of these jerks by upgrading the Transmission Chip with GIAC.
Linky

 

I experience this very very occassionally in my 2005.5 Tip S4. It definitely is limited to very slow speeds, but again, it happens maybe once a month. Granted my car is totaly different than yours, so that means nothing.

 

Okay - well as I drove it to a friend's house yesterday it felt like the car was stuck in 3rd or 4th gear, and when I tried to engage the tiptronic, the the gear display would not show up on the screen on dash. When I enaged into Reverse or Drive - the car lurched pretty hard. and accelerating was painfully slow obviously.

So i took it in this a.m. Here's the scoop: (apologize in advance for not having proper terminology)

The computer for the automatic transmission wasn't communicating properly with the rest of the car computer - so they had to do a sort of "reboot". That fixed it.
Good news: $135 diagnostic fee covered it.
Bad news: I had told them to replace my coolant overflow tank because i noticed it had sprung a leak... they confirmed that, but said my water pump was also leaking and needed to be replaced, along with thermostat. Total for those three to be replaced $1,500 !!! ouch.
They also said my rear prop shaft seal (huh?) - or - rear differential seal was leaking and would cost $800 to replace. Grand total $2,400 and some change.

I'm in Chicago, have to get back to Michigan and for fear of my car overheating I'm having them do the 1,500 water pump repair. I feel like I might be getting suckered... but I'm really in a bind so I have to eat it. I will let my mechanic back home look at the rear differential.

Anyway, for any of you out there who experience the large BUMP --- be observant of the transmission afterward.... i'm positive they're related. By the way-no explanation for why it needed a reboot. Hope it doesn't happen again, but i'm not holding my breath.

 

Good to know, the reboot fixed the issue.
Best time to do Water Pump is when you are replacing timing belt.
Anyway, have a safe drive home.

 

Halfway home the "bump" occurred 3 times... on third one, the transmission was screwed up again. Had to drive the rest of the way home (100 mi) stuck in 4th gear (i'm guessing) at about 60mph to keep RPM's at something reasonable.

Audi at home has much more reasonable labor rate, so I'm glad its there now (the water pump that cost me 1600 in Chicago would have been half as much at home, just due to labor).

Anyway, they're guessing its the Transmission Control Module ---- Audi Chicago quoted me 2,500 which sounds ridiculously high. Not sure what my dealer will charge yet.
If that doesn't do it --- new tranny. 6-10k have been my quotes so far.

I just bought this GD car 6 weeks ago. 25k miles. how is my luck so friggin bad?!

 

I would still suggest trying swapping the T-Chip from some other S4 from same year.
Nothing to loose if that won't work either.