My friend was giving me a jump because my car has some sort of power leak, so the battery dies if I forget to take off the battery ground. The jump went well and the car fired up, so I opened the trunk to put away the leads, while he took them off, and the car died. I asked him what happened and saw he had crossed the leads together. I was able to start the car while it was back connected to his battery, but the electrical for the car (Lights, gauges, everything except the radio for some reason) didn't work. it also is only part of the time responsive to the gas pedal, drives rough as hell, and lurches. When I stopped it it immediately died. I can still get the electrical systems (Lights, radio, gauges, etc) to work while I have the key in, but if I try to start it, they all shut off, and the starter isn't trying. I'm guessing the ECU is fried, ordered a new one... Is there anything else that will need replacing?

 

It's not your ECU.

What are the connections like at the battery? The small red wires attached to the positive terminal - all tight with a good connection?

Have you load tested the battery? How old is it? Is the alternator charging? What's the charging voltage?

 

the alternator seems to be busted, shame because it had a brand new one... the battery surprisingly seems like it might be alright

 

If you have a mutimeter you can test the battery and alternator. With the car off, put the leads of the meter on the battery posts and it should read around 12 volts give or take a volt. Then fire up the car and with it running put the leads on the battery again. t should now read around 13.8 to 14.5 volts. If it does, then the alternator is properly charging. If not, then pull it and get it tested. Hope this helps. Let us know how it works out.

 

A good battery sitting over night should read 12.5 - 12.6 Volts. Anything less either needs a charge or replacement. Doing a load test will sort it out.

 

Yup......pretty much. I've had batteries in the past that would drop to around 11.5 volts overnight and still work ok, but like you said 12V is about the lowest you really want it to go and still be reliable.