difficulty during start-up only: takes a long time, many goes, stalls

[Jinster]

Hi. I have been having this issue lately, was wondering if anyone can shed some light please:

1. The car is sometimes very difficult to start - key needs to be turned for 10 seconds sometimes

2. Sometimes when it starts, the idle fluctuates like a sine wave - initially between 1200rpm and 100rpm, then eventually settles down to normal idle after around 10 seconds

3. The car often stalls during this period of idle fluctuation if the rpm drops too low

4. If I artificially keep the idle up by pressing the accelerator pedal for a minute or so, the car would stall anyway after I take my foot off

5. Once the idle normalises after start-up, the car drives without any problem, no further idle problems, til next start-up

OBD2 pulls no codes.

I have already washed out the throttle body and ICV valve. ICV in particular works fine (opens and closes swiftly) when hooked up to 9V battery.

The fuel pump and filter were both replaced 6 months ago.

Where should I look at next?