engine problems?

ok toyota dudes. i thoughtn knew what i was doing but i guess not. i just rebuilt my engine in my 4x4. 22re engine. i put in new 40 over pistons, trd cam, everything new. i can get it to crank, but as soon as i let off the gas pedal it shuts off and wont start for a little while. i can't get it to run more than about 30 seconds. it wont run long enuf to check the timing. i need this thing running in the next week befor i get my car sold. any help would be fabolous.