Confused about S13 SOHC ECU code

[240_RU]

As I found here http://www.240sx.org/faq/articles/ecmcodes.htm
anyways, i following step by step and came up with code 14 for some reason which is Vehicle speed sensor circuit. I dont think it has anything to do with my problem. My problem is that every time i start the car its shakes with low RPMs around 400-500 and then if I floor it, no problems. Also i dont have a problem starting the car when its worm - starts right up (for ex if i go to the store and come back its gonna start right up). The problem occurs only if the car stays overnight or like couple days then i have this rough start issue. So on the ECU once i turned that thing fully on 180 degrees for 2 seconds and back green light came on once and then the red one blinked 4 times (short) which means code 14..... so im totally confused. What Vehicle speed sensor circuit has to do with starting of the car???? Any suggestions please?