2G Engine stalls when idle

[Doomchild]

Little over a month ago my car started stalling when idle, well... any time I didn't apply any gas. It'd restart instantly but I had to keep the revs up or it'd stall again.
tracing the possible culprit to the IAC I ordered a new one and while I waited I adjusted the throttle valve a bit to keep air going into engine. last week the new IAC arrived and got installed, everything was fine and the throttle valve got put back in its default position.
today, on the way home, I got stuck in a traffic jam and about 15minutes in my engine cuts off... same problem...

either my new IAC just broke within a week or something else is going on. anyone got any idea what might be wrong? there's no engine check light, the car just doesnt idle, rpm drops to 0 and engine cuts off.

 

[Galipso]

adjust your BISS screw on your throttle body

 

[Doomchild]

did that, idles at ~700 rpm cold. engine stalled again on the way to work this morning so either something else is going on or the BISS screw isn't properly adjusted. dropping by the mechanic tonight to get it checked.

either way, the original problem still persists, what's causing the issue?

 

[pauleyman]

Isc needs a range of motion. If you just randmly adjusted biss to get a 700 or 800 idle that isnt correct. Fill us in on what you did when isc was replaced. A bad isc can also take out the drivers in you ecu. Are you sure ecu isnt damaged from your old isc?

 

[Doomchild]

the replacement of the IAC was done by my mechanic, just took the old on out, plugged the new one in and cleaned the throttle body before putting it back in. then readjusted the biss to (what I assume) was its default position, the car ran fine for a week then it just stalled again, no stutter or anything, pushing down the clutch and lifting your foot off the throttle is just like switching the car off, rpm drops to 0 and the engine cuts off.

last friday we just quickly changed the biss so the car didn't stall. did it with a cold engine. ran fine till this morning after driving for 30 minutes it started having trouble keeping it's rpm from tanking to 0 (runs around 300 idle but dips below that when braking and can drop low enough to stall the car).

can I read out the ecu with a default connector? my mechanic is actually a BMW shop, so no specialised gear gonna drop by after work to check.

judging from what's going on, either the replacement if faulty, a sensor is broken or my ecu is acting up.
as for the reason the biss adjustment didn't work, maybe it adjusted itself due to vibration? I drove for several weeks with iac unplugged and the biss adjusted before the replacement part came in and had no issues.

replacement i bought: http://www.benl.ebay.be/itm/171826595965