Hello, been chasing this issue for awhile. Happens every once in a while but the car will rev repeatedly (ex. 1500 rpm to 3500 rpm then back down) automatically on start up occasionally and the increased emissions will appear on he dash.

Now, my friends car was doing the same and thinks it's a clogged egr valve. However from my understanding the gas motor (m54) does not have an erg valve, only the diesel..?
Any ideas where to start looking to cure this?
Car is an 05 525 with an m54
Thanks for your time.

 

Any help?

 

Any mods? Intake etc

 

Very possible it could be the thermostat. My car doesn't rev from 1500 to 3500 rpms but I just brought it in to my friend who's the service manager and after diagnosing the increased emissions it turned out to be a thermostat

 

nope no mods to the motor.


not convinced its the thermostat... i will however look into it some more.
did a slight cooling overhaul and the one thing i didn't change was the thermostat.
how about a DISA valve?