The last month or so my car has started to, for lack of a better word, "buck" under heavy acceleration - sort of like it isn't firing right.. Last yearI replaced the ignition controller and had a new turbo put in about 6 months before that. I thought maybe i got some bad gas so i ran sea foam with my last fillup -- no appreciable change.[/align][/align]I'm replacing the ABS module this weekend so it will be a car work weekend and would try to look at whatever you guys suggest while I'm getting dirty. Don't have access to VAG-COM, etc...[/align]

 

Does it lurch once as you're first accelerating or is this a repeated jolting sensation? Because if it's the former, you might check to make sure your engine mounts haven't gone bad. If they have, they'll leak a purplish fluid and acceleration will be jerky. At any rate, have the car scanned for codes which Advance and Auto Zone will do for free.

 

Apparently there was a better way to say what i was trying to say. LOL![/align][/align]"a repeated jolting sensation" is a pretty good description and it only seems to happen under heavy acceleration.[/align][/align]I should also add I have a K&N filter -- possibly a dirty MAF or something? Seems like that might not restrict the problem to heavy acceleration circumstances though.[/align]

 

I havent had my a4 long enough to mess around with the boost but, i used to own a turbocharged talon and if i had a large boost leak it would hit fuel cut and jerk violently, as if i hit something.

 

a leak is my main suspect and i hope that's all it is (your description seems to fit). seems to happen at the end of winter when the old hoses get brittle from the long cold winter. happened like that two years ago like that. i'm taking it to the garage on monday for a look if I don't find it myself -- just trying to get other ideas of potential causes. i have a shop that has treated me right in the past, but i feel like you should always show up at a mechanic's with an idea of what's happening. i'm probably also going to seafoam the top of the engine tonight or tomorrow.[/align]

 

i just thought of what it reminds me of -- i had a '83 BMW 533i some years back that had a lot of torque and it was very prone to tearing up flex couplers in the drive-shaft. it starts out only doing it under hard acceleration, but does it more as the coupler gets worse. i tried to look at the A4 drive trainbut it's covered by heat shields that i don't want to remove for an exploratory mission without knowing if what i'm looking for is there.

so..... does the B5 A4 have a flex coupler in the drive train????

 

sounds like a vacuum leak. check your hoses

 

found one check valve that looks bad, but no major leaks were apparent. hmmm? guess i'll have the shop look into it. i hope it's something minor.

on a side note, i swapped my ABS module out lastnight and it's not that bad of a job. Probably took 1.5 hrs and the remfg part from modulemasters came right on line with zero issues. it's nice to have those damn flashing lights off for the first time in 8 months. now to get the stupid airbag light off!!!

 

answer was a check valve and two new coils...