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.
im Also awaiting a new distributor to get here for a hesitation and stutter when accelerating

 

for reference, this is where I welded it to. This part under the rear bumper

 

Based off your post history, your car was running bad for over a week now. I doubt welding on it today caused that. Have you done a full tune up? what troubleshooting have you done to rule out fuel pressure, vacuum leaks, worn ignition, faulty sensor, etc?

Your exhaust probably sounds odd and weird because whatever "work" you did to the exhaust made it worse. It's hard to tell exactly what you did based on the video but it looks hokey just from seeing the back of the car. you've also made threads inquiring about "straight pipe verse header dump for pops" so I don't really have much faith in whatever you were trying to accomplish. You also claim you're "extremely new to welding and working on cars" which isn't exactly a recipe for a good flowing and sounding exhaust. The exhaust is supposed to be able to move separate of the car's body and only secured with hangers, welding it to the frame is a big no no.

I don't mean to sound like a jerk but I think you're on the fast path to hacking this car up. Put the welder down, stop worrying about making the exhaust pop and burble, give the car a tune up (plugs, wires, cap, rotor, air filter, fuel filter, etc) and see how it runs. If it's still running poorly then start familiarizing yourself with the car's fuel injection system and how an engine works in general, then start researching your symptoms and how to troubleshoot and rule things out.

Address why your starter isn't disengaging correctly. It's normal for lights to dim when your starter is drawing power.

I've welded on my car many times without disconnecting the battery. Could it potentially harm something? yeah. Is it good practice to disconnect it first? yeah. I think we've all done it hundreds of times without issue but you have to have the ground clamp secured to what you're welding so the current isn't traveling throughout the car's electrical system looking for the welder's ground.

 

I appreciate the concern and the advice, but this car is a project car I bought for two grand. I’m using this car to learn how to work on cars and it was way more hacked up when I bought it than it is now lol. I’m a teenager so I’ve got all the time in the world to learn lol. As for the exhaust I wasn’t really trying to accomplish anything other than getting it to stay on, and as for the post I was only curious because I have a friend with the same car and his popped way more than mine. I’ve got a new distributor on the way already and if that doesn’t help it’s back to the drawing board lol. I appreciate the help but im just a 17 year old with a shitty project car held together by rust and prayer