Idle problem during cold start

[glen-sj]

I have a 1995 530IA with 68K miles. I've experienced lately during some cold engine start in the morning, the idle start around 900 rpm for the first 5 seconds, then the idle would drop down to around 500 rpm for about two seconds then rises right back to 800-900 rpm . There seem to be a load being placed on the engine causing the rpm to drop. Is this normal? Is there a component(s) that kick in right after startup causing a load on the engine? Would a bad ICV or CPS cause this? The idle do gradually drop down to around 500-600 rpm as the engine start to warm up. I've looked and made sure the A/C is off during the cold starts. Otherwise the car runs ok. I've replaced the spark plugs and O2s.

I also have a 1992 525IA and it never encountered this problem.

Any ideas what is causing this and what need to be done?
Thanks.