I have an '04 M3 with a standard transmission. My battery recently died and after I jumped it, i started noticing all kinds of irregularies with my car's performance. That morning on my way to work, the engine was idling funny.Every timeIwould come to a stop, the engine would almost stall (rpms less than 500 on the Tac) and then the engine would rev up to around just over 1000 rpms. I let the car sit for a few days and tried it a few days later. It still had that problem but not as frequently. Then it was almost non-existant but the engine was idling much lower than it usually did. Last weekthe almost stall out thinghappened again so I decided to take it to the dealer where i bought it to get it serviced. They told me the battery was bad and that was what was likely causing the problems. I had a few other issues that they took care of. The next day i took the car back to my office which was less than 4 miles from the dealership. As soon as i pulled into the lot, the car almost stalled out as i pulled into my space then reved up again. I took it back to the dealership and they put in a new throttle body. I've only used the car two days since then and I haven't noticed any problems until this morning. While driving to work, i heard a loud pop. I was the only car on the road at 5:30am and i didn't notice anything lying in the road that i could have hit. I pulled over, got out and noticed something under the hood making a loud hissing noise. My engine definately sounds louder than it used to. The car is only 4 and a half years old and now sounds like it's 8 or 10. When i got back into thecar, i pulled to a stop light and accidently took my foot off the clutch while the car was in first gear. It stalled out but it didn't stall out like i've noticed in the past. Usually when i stall there's a substantial forward jerk. this barely jerked at all.

Sorry about the long-winded description. I'm really worried about spending any more money on exploratory mechanics. If anyone has had a similar experience please respond. thanks.

 

Did you ever figure out the problem?...I've had a similar string of events with my 04 Mazda 3 automatic. While driving 2 months ago, the rpms started going crazy and the car stalled. It took a while to restart and then stalled again. I got it to the dealer and they said that the battery needed to be replaced and the computer reflashed because there was a service bulletin that matched the rpm/stalling problem. A couple of weeks later the same thing happened and this time the dealer decided that the throttle body needed to be replaced. Now another month later the same thing happened again (just the strange rpm behavior, no stalling so far). It is back at the dealer now, but I am not optimistic about them figuring it out. My engine also sounds a lot louder than it used to.

 

Check your vacuum lines.