Green’s Dictionary of Slang

flooey! excl.

(orig. US) an echoic excl. designed to resemble the sound of an explosion.

[US]T.A. Dorgan in Zwilling TAD Lex. (1993) 37: And I tried to get under it and flooey — I didn’t.
[US]H.C. Witwer Fighting Blood 270: I took aim at a tree about a mile away, set myself, and – flooey. I don’t even get a foul!
[US]Howsley Argot: Dict. of Und. Sl.

In phrases

flooey in the filbert (adj.)

eccentric, unbalanced.

[US]Ade ‘The New Fable of the Intermittent Fusser’ in Ade’s Fables 59: He was on the waiting list for the Nut Club. Our Old Friend was flooey in the Filbert.
go flooey (v.)

(US) to go wrong.

[US]Wood & Goddard Dict. Amer. Sl.
[US](con. 1914–18) L. Nason Three Lights from a Match 162: I seen it go flooey off the road while I was duckin’ fer that shell.
[US](con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 568: He’d like to have seen Martin get wise before [...] his heart had gone flooey on him!
[US]R. Carver Stories (1985) 320: It was bad luck that their fridge had gone flooey.