M3 engine problem

My good friend has a 2002 M3 with 50k miles, and it just started a serious engine problem which the dealer can't seem to fix. The car bucks and hesitates like the spark is cutting out or gas is not getting to the engine. The amazing part is the dealer had the car 2 weeks, originally tried to wrench $4000 out of my friend to repair, finally settled on $200, it's still under warranty for the engine, they tried to say the problem was not on the "engine" but some manifolding or some such BS. Anyway the dealer said it was fixed, after 2 weeks in the shop, it was doing the same thing the day we drove it out! This isn't your shade tree mechanic folks, this is a big city BMW dealer in Houston, TX. I told my friend he can borrow my sweet purring Olds 88 LSS with 130k miles any time if he needs a ride while his $55k M3 is puking out its guts.

We can't tell if it's a computer issue, spark problem, fuel problem, whatever, but if their mechanics don't know, we're clueless. Anyone else see this problem, my friend will be eternally grateful, and not have to endure the endless harrassment from his co-workers on the third reich mobile.

This is most likely a sensor problem. Whatever you do, don't listen to the dealer; thier job is to make money. While I have made the mistake of not listening to the dealer in the past, the bigger mistake was not listening to my tools. So get a obdII scan tool, if you have the money you could get a really specific e46 one, but it will most likely tell you what is wrong. You could also check to make sure that the o2 sensors didn't come unplugged or something like that.

Dont waste your money on a tool that is not going to tell you whats wrong with the car. The dealer has already read out the fault codes of the vehicle and obiviously none of them were the problem for the rough idle. If the problem hapens again, take the vehicle back to the same dealer, they wont try to fix things that they know arnt broken.

You may just need an ignition coil. If you have a bad coil you will feel all those symptoms. BMW redisgned the coils to avoid problems they have been having like this.