There is a possibility that the problem is in the ECM You may need to reset the modual . What is likely happening is the modual memory was corrupted by a bad voltage regulator as mentioned by @jayeff . Try this as a fix disconnect the battery and turn on the headlights and leave the car for a good 2-3 hours . This is to drain any residual power from memory of the ECM. Then reconnect the battery and start the car let the car idle for 10 minutes before touching the gas . Its very important that you don't rev the engine during the ten minute idle as the ECM is reprograming itself .For the next little while the ECM will be learning your driving habits so drive it similar to breaking in a new car . Before doing this though it would be a good idea to check the engine codes as mentioned by @oldturkey03 this way you have the codes as resetting the ECM will delete any engine codes. Hope this helps