which vac lines need to be hooked up and where are they located for the ls1? my car wont idle correctly unless i hold the gas pedal down a little otherwise it dies. any ideas why its doing this?

even with a vacuum leak these motors will still idle. the only vacuum sources off the ls1 come off the intake manifold. There is 2 on the front pass side of the throttle body (1 runs to the pass front valve cover) (and the other runs with the pcv system already hooked up on your motor. The only other vacuum comming off your motor come off the back center of the manifold. One is a big vacuum line that runs to your brake booster, the other comes off (small line) and is what runs your hvac controls inside your car, thats it.

When your car runs, does is sound strong or really weak? If you missed a ground on one side of your coils the motor will run but only on 1 bank of cylinders. that might be your problem. vacuum shouldnt be giving you any problems

If you suspect a vac issue, cap it all off. See how that works for you. Check the MAP sensor where it seats into the intake. That seal stinks on the FAST intake...but its supposed to be better on the stock intake. Check it out anyway.

But I generally agree...it should run and idle on its own even with the biggest port left open. You are either not firing on all cylinders, or one of your sensors isnt working properly. Really gotta start systematically checking it all out.

J.

One question did you have the battery disconnected if so the first time you start the engine will not idol, the computer needs to relearn the idol so shut the car off and restart it.

i have checked the vacuum lines and capped them off. I have not disconnected the battery and it is still not idling correctly. its firing on all cylinders ( i think) because it runs fine if i have my foot on the gas just a hair. it surges when i let off the gas a couple times then dies. could it be the BISS screw needs to be adjusted? i noticed the air intake valve completely closes when i let off the gas so this in turn would not allow any air to come in the intake, would that cause my issue?

It really could be anything. Bad MAF, bad IAC, sensors not getting 12v while its running... What is BISS??

What all has been done to this motor from the time it was last running in a vehicle to now...? I cant recall what, if anything, you modified.

J.

Base Idle Set Screw = BISS i have not modified anything to the engine. just put it in and go. i followed team third gen wiring setup and that was it. had it tuned by andrew. nothing else was changed.....

i still think your problem is something simple. Your motor ran great when we pulled it. your ecm worked great when we tuned it. since your motors all stock, you shouldn't have to change anything. i would pull a wire on each side of the motor and make sure your firing on all 8 cylinders. only other thing i could think of would to be check your fuel pressure and make sure its correct.

Right... Like andrew said. Nothing should need to be tweaked mechanically like the idle screw. I know you said you followed a wiring write up. But along with checking what andrew said, i would still be making sure each sensor is getting the power it requires. I made this mistake with my maf sensor. While sifting through all of the spaghetti, I accidentally cut a pink wire that killed a whole circuit, and didnt realize it until I got check engine lights for the MAF and O2 sensors and whatever else was on there.

Ide like to hear how it runs when you put your foot into it to keep it going. Does it stumble? Struggle? Can you post a vid of what its doing?

Andrew...what all did you do when you tuned the PCM...also how long was this motor sitting around before it was fired? The second question pertains to the fuel injectors. Mine were pretty clogged up. The inlet baskets on two of mine were completely closed. Caused major idle issues and low power. And mine hadnt really sat that long.

You'll get it...it cant be anything too major.

J.

the motor probably sat a few months before he fired it. As far as the pcm is concerned, we just did a bunch of simple things. tuned out a bunch of codes for things we deleted (air pump, egr, tank purge, etc). tuned out vats, did bump the timing a tad and a few other small things. We ran the ecm in the car i used to tune the ecm and it worked great just to double check everything i did before i shipped the ecm back. I still say he has a circuit somewhere without power. The only thing i've seen with these motors not letting them run is either low fuel pressure, or only running on 1 bank of coils.

I've sugested josh check spark on both banks of the motor, and check all his power wires to the ecm but im not so sure hes doing any of these things.

I think Ive expressed the importance of checking the pink wires for power a couple times also. It doesnt take much. There are lots of junctions and what not in the stock harness. And once you start to try to simplify it, its really easy to kill power to a whole circuit, while not even realizing it. Gotta get that multimeter out and start probing.

My motor has never "not idled". Even after sitting for months and months, it still fired on the first twist of the key and idled just about perfect. And I changed things like throttle body and exhaust stuff before I fired it for the first time. Even with two of my injectors completely clogged, and two others partially clogged, it still idled. Rough...but idled.

If he was having a fuel pressure issue, I would expect it to idle, but not want to rev. He says it revs and stays running with his foot on the gas...but I dont know how well its running. If its barely clinging to life, or revving perfectly fine. If its revving great, and sounds great, but just wont idle, then its something in the idle circuit. If its revving like a slug, and sounds sick, then he's missing ignition or has a fuel shortage or something.

Its just one of those things that you cant really do much about over the internet except offer suggestions. Hopefully he sorts it out...sounds like he's close.

J.