recently purchased my 318i. After miscellaneous work (new thermostat, checking for air leaks, breather hose replaced, oil change, vacuum pump oil leak repair) I've got it running nicely when she is up-to-temperature i.e. temp needle is verticle, middle of the scale, 12 o'clock.
But, until that point is reached she runs unevenly. After an initial period of 30 seconds or so following start, the revs drop to 700ish and a regular thruming begins shaking the engine (2 thrums per second). The car is difficult to drive like this; tries to stall at low revs, feels like weak mixture.
So I was wondering what the order of events is after starting, during "warm-up".
1. The initial 30 seconds, idling at 1000rpm ish - smooth, all ok. What is controlling the idle? Throttle? VANOS? Valvetronic?
2. The time till full temperature is reached - uneven idle. What is controlling the idle? Throttle? VANOS? Valvetronic?
3. Normal operating temperature - fine, even idle 700rpm What is controlling the idle? Throttle? VANOS? Valvetronic?
I've read that the throttle controls things "until warm". But I'm not clear what "warm" here means.