I have a 2000 540i automatic. Today while on a long trip my car started to act funny. I lost the accerleration that im normally used to. When i hit the gas it started to bog out. then the check engine light came on sfter a bit then it really got bad the car started to die. I pulled over shut the car off for a minute then started it back up and it runs fine. The check engine light is still on. I dont think its the tranny, because im not getting any warnings. any ideas, could it be the mass air sensor?

Maybe.

You need to find out what codes are set using a scan tool. Places like AutoZone might do that for you. That will give you a clue where to start.

oh one more thing. I noticed my gas consumption go from 24 to 16 mpg in an instant.

..

get the codes read, this is not a 1952 chevy. The car knows what is wrong with itself in most cases. Go to autozone or advance auto and have them read the codes. save the codes they give you and enter them in this thread, then maybe we can help.

fellas, got the codes:

P0174 and P0171 too lean...

Also the service engine light went off yesterday on my way home. It seems like this problem only occurs on long trips. Usually after 3 hours of driving. Thanks for your help.