My current ride is a nice little 535ia with a great, tight engine. 120k miles. On previous 3.0 (e12) and 3.5l sixes I have owned the starting was characterised by a quick blip of the starter and then the motronic would take over and get the motor going.
My current 3.5l takes a 3 to 5 seconds to "catch" if I don't throttle it. If I don't give it any throttle, it will catch slowly, firing weakly, and then slowly it will increase in rpms until it is idling. Sometimes, with no throttle, it will stall on the 1st try. If I give it some throttle, it will catch quickly and then the motronic will keep it going. Sometimes the rpms will drop way low and then the motronic will juice it to get the rpms back up and keep things running.
It does this whether it is cold or hot.
Once running, the motor runs and idles great.
I'm not complaining if this is the characteristic of this particular motor, but I would like to fix it if I can. What could be causing this starting issue?
no vacuum leaks
good fuel with redline cleaner
otherwise in tip top shape