Quote Originally Posted by z5367489 View Post
Q1: Yes, after certain observation, it happened when engine is warming up, cold start is usually normal.
Q2: I think so....
Q3: idle in cold start is ard 1000 -1100 , fully warmed up 800-900 and i realized it shakes a bit, not stable.
From what you've said, I'm inclined to agree with trism (post 6), something in the IACV/cold start function/throttle body etc. The IACV in particular controls more than just the base idle (in fact the base idle is controlled by an air bleed screw), it's function is in fact to compensate the idle when loads are placed on the engine by such things as the A/C, engine cooling fans, P/steering, anything that would cause the engine to drop below idle speed. It is controlled by the ECU and sensors and there could be a fault on that side of things. (it's water supply is only to prevent it freezing up in very cold conditions)

Have a look at this, it's a long read but you might get some clues from it
http://ecomodder.com/forum/showthrea...ained-967.html