Help! Engine Dies during braking!?!

Sounds like it's time for a new battery. If the old one died and you have to jump/charge it the life expectancy is only about 2 weeks. The battery not only provides charge to start your car but also it acts like a load. Think of it this way: when a battery dies it's not like it has no charge left (i.e. you could start your car right up when it stalled out on you at a stop light/sign), it does. What really is happening is that the battery is shorting out and when it does that there is no load for your car to run the necessary functions like engine management, speedo, odo, etc. You have to replace the battery anyway because it died but I'd bet that if you took it to someplace like Sears and had them hook it up to their testing machine, they'll tell you that you need a new one. Hope this helps.

Edit:The Monster Cap that you have in there probably isn't helping the situation either...try first without the cap then if all goes well, let it run for a bit to see if you have any further problems before hooking up the stereo.

were you crankin the tunes? leave off the radio and hit the highway to see if the alt will charge the battery up. If it won't hold the charge its time for a new one. Do you leave the car sit for long periods without driving? If so invest in an optima yellow top.

This sounds just like the problem I have. I was told to replace the IAC, which I did and it didn't help. I put a new battery in it and that didn't help either. Let me know what fixes it. I want my damn stang to run again.

How many amps is your alternator? Seeing as how back when I was in to car stereos people didn't use 2 batteries, I wouldn't know, but the fundamentals of charging systems would say that one alternator at stock amperage probably ain't enough to keep up with 2 batteries.

Edit: And greetings to a fellow Tucsonian. I'll be on the lookout for ya around town once you get it running.. I think have the only black '04 GT coupe in town.. say hi if you see me.