I have a 2003 c5 z06 .. I just swapped motors and I'm having some issues.. 1st issue is I can't get the car to stay on ... it will start up fine but then shut itself off

I blew my ls6 up and replaced it with a ls1 with ls6 heads and cam

Replaced every senors on the block

Installed ATI crank pully 10% smaller then stock

A/C delete

Installed headers and x pipe

Vararam intake

Brand new optima battery

New spark plugs

Red spark plug wires

Some days the motor starts right up and idles fine and other days it doesn't even want to start


My 2nd issue is now my interior lights are staying on ..and when I hit my brakes my dash ,radio and ac controls come on but brake lights don't work ... if I put my hazards on all interior lights flash with the hazards...and if u do get the car started .. if u turn my lights on the engine shuts off


I appreciate all the help

 

Wow... could be a lot of things. On a motor swap, you have to check so many things. I had this happen after my first round of mods. My car ran fine after the mods, then one day out of nowhere, it would start up but die immediately. Eventually figured it out with some testing. I had fuel pressure when the key was turned to start, but when I released the key to the On position, it would lose pressure and it would die. It would start right back up but again die when in the On position. I was able to drive the car by jumping two spots on the under hood fuse box (fuel pump relay) which gave me constant power to the fuel pump when the key was in the On or Start position. My issue was found to be a bad ground wire on the fuel pump (where it connected to the frame). Enough of that...

For you, the first thing I'd do is check your error codes and start troubleshooting from there. Since you've done a motor swap, I assume you know how to check your error codes. Some basics you'll need to check are your grounds and connections and a mechanical check of your fuel pressure. The error codes should point you in the right direction. An intermittent ground could also cause your issue. You'll figure it out, just be diligent.

 

Thank you I will check the fuel pressure this weekend the only code I'm throwing is p0300

 

Ok, well that's a start. p0300 is a misfire code and can be caused by a variety of things, worst case being a broken valve spring. Could also be caused by broken plug, bad plug wire or connection, melted plug wire, etc. Sometimes plugs get broken installing headers. Make sure you've got your O2 sensors correctly wired and double check to make sure they're not grounded anywhere. You've got a little bit of detective work to do. The code is a starting place but you're going to have to check all the possibilities until you find it. That last part where you mentioned the lights and other issues almost assure you have a wiring problem somewhere. Turning on the lights should not kill the car. Battery voltage is another issue you need to be sure of. A weak battery can cause all sorts of havoc with our C5s. Be diligent and thorough. You'll find it eventually and wonder why you didn't see it earlier. Pay special attention to every one of the disconnected then reconnected electrical plugs while you were changing out the motor. Could easily be one of those. Inspect the wiring for shorts and ground problems as well.

One other thing to check. Make sure the bolt for the ground strap on the back of the passenger side head is tight. A loose bolt here will cause some of your issues with "sometimes idles fine, other times won't start". Just a thought.

 

So many times this happens. The bolt on the back of the head is not tight. Simple, but easily overlooked.

 

The most elusive electrical problems are almost always grounding problems.
Check the grounding strap under the steering column , The ground on the rear of the passenger head (as mentioned above), and the ground near the starter.

Check the red wires going to the main fuse box. One of them goes through the firewall to the internal fuse box.

Also check the wire harness connectors on the outside wall of the battery box area to make sure the colors match up on them. I could only imagine what would happen if the lighting harness was plugged into the transmission (not sure if that is possible). Some people can be slightly color blind and not know it. If that is you then have someone else check.

 

How fast does it shut off? If it stalls right away it could be a vacuum leak. If it's a leak its most likely related to something at the back of the intake.