Thanks for any help in advance. So today I took it upon myself to weld up a new exhaust to my 2.8 liter (fuel injected). Here’s where the problem starts. I am extremely new to welding and working on cars and I welded the exhaust up to the frame to try it out (I figured if it drones or something I can just redo it) and I forgot to disconnect the battery at all. My car wouldn’t start after this and I had to charge the battery (which stopped charging at 62%, maybe unrelated). Then when I finally start the car something feels off. The exhaust sounds odd, it’s kind of a steady pulse of warm air now instead of a flow of hot air, it sounds more choppy like a vacuum leak and idles at 5-600 warm(video attached), and the starter isn’t really disengaging correctly, and when starting the car, the interior lights flicker! I’m wondering if im just paranoid and these things all happened before and im just now noticing because of the new exhaust install or if I really screwed something up.

 

for reference this is what the exhaust is welded to, the part with all the rust right behind the rear bumper

 

You may not be. Get the battery. load-tested and fully charged!! We've enjoyed odd issues with a slowly dying battery (longer crank times, starter not completely disengaging after start), that were completely solved with a new one. That's even with the car always connected to a Battery Tender while stored in the shop.

 

I also frogot to disconnect the battery several times when doing welding on the car and it never caused problems. Your battery is probably going out or there's an electrical connection issue.

 

As an aspiring wrench turner I did that once or twice. Had it burn up ground cables everywhere once. Battery may be shot from taking the current if it had to travel through the cables if your welding ground lead was not clean and close to your weld.

Chuck a known good battery in there and do a voltage drop test for both the positive and negative cables, check or replace your ground straps, and next time ensure you have the battery disconnected and solid clean welding surfaces and ground connection.

 

Did you weld the pipe directly to the frame?