The car sat for about a month or more. Had to jump it. It took a few seconds after started to idle up. Then if i gave it a little gas, when coming down it would go down to about 500 rpm. Then go up. Did that for a few minutes. I started playing with it and i unplugged maf, seemed like it didnt change how it ran and didnt turn on check engine light. Then i unplugged maf, tps, iat and it still didnt come on.. Shouldnt the light have came on? Ita a 99 ls1..

It would come on after the engine ran long enough for the pcm to pick up that something was not in specs.