mustang died...again

I'd replace the battery and then see if the secondary problem is cured....if not, worry about it then.....but yea i guess it could be something with the alternator......

From you description, the car will restart without any problems if it is jump started with another battery.

Make a trip to AutoZone or Advance Auto Parts or whatever auto parts chain store is near you. They will check the battery and charging system while it is in the car for free.

You need a good battery to make the alternator work properly. A bad battery will not provide sufficent power to engergize the alternator field windings. That will cause the alternator to not put out the voltage needed to charge the battery and run the engine.
Connect a voltmeter across the battery terminals and run the engine. You should see 13.8-14.2 volts at 1000 RPM.

If the electrical system checks out good, see the "Surging Idle Checklist for help with all your idle/stall problems. Everything you need to find and fix idle problems is in there.

The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

One of the first steps in the checklist is how to dump codes. That is the place to start.

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The solenoid valve located on the back side of the passenger side wheel well is not functional. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

With the with the ignition on, look for 12 volts on the red wire on the solenoid connector. No 12 volts and you have wiring problems.

With the engine running, stick a safety pin in the LT Green/Black wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the cats. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Putting the computer into self test mode will cause the solenoid valve to toggle. If you listen carefully, you may hear it change states.

Code 83 is an EGR fault that I have not seen before and have no definition for. I suspect it is an open circuit in the EGR vacuum regulator solenoid coil.

Disconnecting the battery for 5 minutes will clear the codes. So will removing the test jumper once the codes start to dump. If you haven't fixed the problem that caused the codes, they will come back the next time you dump them. Don't forget to do the engine running codes too.The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Work your way through the "Surging Idle Checklist to find and fix the rest of the idle problems.