Engine Problem need help

[DeadShot]

my last engine seized due to flood water

so i replaced the engine with a 99 automatic engine everything was the same on my 98 engine

i got the new engine and clutch in

fired up the engine and started

itll only start if i give it full throttle and let go off the key
but check engine light comes on and the fan kicks in straight away even tho the engine is cool

when the engine is warm the car wont start

 

[frank]

sounds like a coolant temp sensor problem