just got my gsr started, it is its first ever startup and i put a p28 stock ecu obd1.. it idle normal for maby 5 seconds and jumps continuously from 500-1800 rpm...

whats going on?
also wont let me rev up the engine at all it will shut off.

 

p28 is for d16z6, i dont think that ecu is meant for your gsr, unless it has been chipped, which it isnt. You should check on your iacv, or fitv. have your bleed your coolant system?