318 won't go past 15 mph

[bmwhartgeM3]

It is possible the crank shaft postion sensor, does it sputter to 15 and rev out of order?

[xxxJohnBoyxxx]

Any national chain auto parts store will scan it for free. Get a list of the codes and post them here or google them.

Limp mode does exist on the Motronic 5.2 since I have caused my motor to go into it on a multiple misfire situation by running too much boost with no meth/water. Mine corrected within 15 seconds but if you have a bad sensor it will remain in "limp" mode to protect the engine. I can tell you it's not knock sensors, O2, SAP, TPS, EVAP purge since these will not cause a limp. Major pre-ignition, multiple mis-fire caused mine.

Maybe a crank position sensor but only a guess.

Please start with the easy stuff. before looking for the big ticket items

1. Is the throttle body butterfly opening all the way when you push the gas petal all the way down as Jess suggested?

2. Is the traction control TB jammed in a closed position? or activating when it shouldn't?

3. Auto transmissions have two speed sensors in them and when one goes bad it tells the DME to "limp" so you have to take it in for repair so you don't get stranded on a railroad track (OBDII American cars all have this, probaly German too but not 100% sure)

4. Will the car rev freely in park?

5. Have you disconnected the battery and opened the door to discharge the caps, then re-connect the battery? This will clear all code since they are held in RAM memory. Adaption value will need to be learned again so expect the car to run a little funny for 5 miutes but see if it will drive over 15mph until the codes re-appear.

Get back to us with the easy stuff and we will try to help you get this solved.

John Smith