In a previous post about this subject, I explained what I did to find the culprit of this strange problem; Swapped and cleaned the Idle Air Control valve with the one on our other M3W. New throttle cable. Greasing the throttle pedal and disconnecting the battery. I swapped the Oxygen sensors with our other M3W. All no result.
The last what I could think of was the ECU. So today, I swapped the ECUs of the cars, but also this didn't solve the problem. So, where to look next?
To make the whole problem even weirder, this is what I experienced during my test drives: The idle remains for about 3 seconds at around 2400 RPM when coming to a stop. When at a standstill, it drops to normal idle. When the car is rolling and putting the gear in neutral, the idle remains at 2400 as long the car is rolling; when it comes to a stop, the idle drops to normal after 3 seconds. I even did this rolling downhill for +/- 2 kilometers, and all the time, it remained 2400 steady till to a stop. Then I drove UPHILL. Stopped. Idle was for 3 seconds 2400 and dropped to normal. Released the brake and the car rolled BACKWARDS during this; the idle went up by itself to 2400 RPM! I didn't touch anything! Only let the car roll backwards. I did that several times and every time same result. To make it completely weird, some moments it is all normal again! Even when rolling and putting the gear in neutral, the idle goes directly back to 1000. I did it several times in a row. All normal. And suddenly, the same weird idling problem started again. This above behavior happened with both ECU's. So where to search next ?? Any suggestions ??
