1985 Jaguar XJ6 Engine stalls or goes crazy

Engine Performance problem
1985 Jaguar XJ6 6 cyl Two Wheel Drive Automatic

I have the 85 Jaguar XJ6. It recently started stalling as soon as I started it. I checked the maf and relays and oxygen sensor, and fuses. Anyways, I finally got the bright idea to have someone else start it, and I took off the negative side of the battery. Well, when I did it, the car actually stayed running, but the lights in the car went real bright, the guages all flipped out and when crazy, and the milieage guage started counting like it was driving, and there was this horrible sound screeching inside the car like a bad radio frequency or something. By the way there is no radio in the car. I let it run for a few minutes that way, and then shut it off. I put the negative side of the battery back on, and restarted the car. Instead of running for a few seconds like before and shutting off, it stayed running for about 2 or 3 minutes, before shutting off. But all guages when back to normal and the sound was gone. It only happens when the negative side of the battery is off. However, the car will still not keep running. Can I have a clue why my car is acting slightly possessed? Lol. Anyone?
Thanks.