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..... http://images.nicoclub.com/forums/images/smilies/werd.gif so im totally confused. What Vehicle speed sensor circuit has to do with starting of the car???? Any suggestions please?

[240_RU]

i will probably have to write this down:

the timing kit was purchased from Ebay but chain guides are from Nissan and we replaced it like 5k miles ago never had problems about that

also the car has OBX header from ebay also with brand new O2 sensor from nissan

fuel filter, all fluids, have been changed like last summer when i got my second s13

im thinking MAF cuz i started having these kind of problems when i replaced stock air box with autozone filter and the adapter from Ebay

but stuff like thermostat, radiator, plugs, wires (NGK) coolant temp sensor i changed liek couple weeks ago.......... still does it

Ill go ahead and check all one more time tomorrow but the thing is i can check it only once ..... once the car is wormed up it start right up doesnt matter how many times u will turn it off and on... But thanks for help guys!