after 3 days wont start

[kars]

got truck from auction.once running and warm runs ok starts eazy enough let sit 3 days and wont start 2 or 3 cyl.s maybe hit pulled codes came up with ecm internal error replaced ecm.when wont start cond.happens if i keep on trying to start hopeing not to burn starter up i will get a no [ef] signal code well. going by alldata except no breakout box i removed w/well and ohmed both sig.and return from idm to ecm both zero res.reconnettced trk fired 2 days still fireing but a little worse most time if i start every day it will start let set 3 days and dead when it finnally kicks at first still a few misses i can floor ac.pedal and nothing happens give it warm up time and it will start to work i replaced oil temp sensor iam going to mess with it over the weekend at least get it started agian.any help would be welcome today replaced cam sensor still no start .