Installed engine, Starts, but won't Idle

[ABrider]

Just installed engine after doing a timing chain replace, using otc 6488 according to instructions by Ford. installed engine, started motor with exhaust y-pipe not attached as i am waiting for parts to reattach after having to cut the manifold to y-pipe bolts off due to rust. motor will stay running with foot on gas, but will not idle at all. no dtc's on scanner. do these engines need exhaust backpressure to stay running, or am i looking at another problem?

 

[SoHK_alumni]

Could be the lack of an exhaust but I'd 1st suspect a large vacuum leak.