Well i have everything hooked up and i am trying to start the engine and it turned over like for 2-3 seconds. It almost sounds like not all cylinders are firing or something it just sputters trying to start. i replaced all the spark plugs. i dont have a cold air intake on there yet just the maf hooked up and i dont have the throttle cable on it yet. any suggestions as to where to start?? i have power to the pcm and all the correct wires hooked up.

Take a fuel pressure reading at the rails during cranking and report back.

you might need to give it a little throttle when starting it for the first time. The ls1 will have to do an idle relearn.

make sure you power up the fuel pump .
mine took a while to start . i just added direct current and ground to the pump to bring the fuel forward

What about the IAT? Do you have that plugged in and sitting somewhere near the maf? Is it running for the 2-3 seconds? Or never actually firing up all the way.

Make sure you double check your injector wires and coil wires. If it sounds like its misfiring, you'll have to start tracking that issue down step by step. Make sure the injectors arent clogged, make sure nothing is leaking, get out the multimeter and start checking the plug wires and what not.

Just start with a basic checklist of all the parts and wiring. Make sure its all plugged in. Check 3 times. Make sure all the wires that are supposed to have power have power...and not just by looking at wiring. Check with a multimeter. A broken pink wire will make your life miserable. Make sure there is fuel getting up into the fuel rails and you have sufficient fuel pressure. Check the ground for your fuel pump (this gave me fits when I first started my second swap. bad ground under the rear seat for the pump). Then, start looking at components. How'd you handle vats in the LS1 PCM?

J.

i had the pcm tuned by andrew (previous reply) and the vats was tuned out. I can crank it and the car comes to life for about 2-3 seconds then dies. it sounds like not firing on all cylinders but its not running long enough to make a correct assumption. I just bought the new spark plug wires so i will install those. i hooked up the throttle cable also so now i have control of the air. i will run through with a multimeter to make sure power is where it is supposed to be. what signs will i be able to tell if it is not getting enough fuel? or an o2 sensor is bad? I can hear the fuel pump prime just fine but i will double check the ground to make sure..... thanks all of you for help in this final hour!!!

How about this:

it fired and ran now! just changed the spark plug wires and put the throttle cable on and sucker fired and ran for about a minute till i shut it off! i had to keep on the throttle a little, maybe around 1-1.5 k or so but at least its running! woohoo! another happy ls1 owner!