I'll explain what happened in order

1998 Honda civic dx hatch 5 speed 100% stock just a aftermarket head unit installed 3 months ago.

On Monday I was driving to work and the speedometer just dropped to zero, cel immediately came on, scanned at work code for speed sensor. Ordered that

Drove car all week without a problem. On Thursday I went out to dinner, noticed my radio had reset as if the car lost power. Drove to dinner, no problem. Come out to leave go to start my car dead battery. I pop start it and it's just sputtering and misfiring, dim lights. Stalled out. Pop start again and it runs the same. If I give it a slight bit of gas it'll get going so I attempt to make it home. If I turn on the lights the car shuts off as if it was on a switch, eventually I lose more and more power, misfiring gets worse and it stalled out. I jump started it, ran absolutely fine rest of the night, started right up the next morning, drove all day then died again.

I replaced the alternator, let the battery charge, car ran fine idling for about 10 minutes and died when I flipped the lights on.

I'm stumped, I would appreciate any and all help I can. Thank you in advance

 

YOu're having issues with the engine harness, you need to check those dead plugs behind the intake manifold.

 

I'll check that out later. Any other suggestions