Q: replaced the starter. went to connect the negative battery terminal, the starter made a whirring sound and sparked at terminal.

Electrically, there a couple scenarios that can account for this, all equally odd, but if you were not having any problems with the car’s starting circuit prior to replacing the starter (i.e., just the starter motor failed) and you have hooked up the starter correctly, the starter motor you installed is probably internally miswired such that you were able to complete the circuit to the motor when you touched the negative terminal of the battery to body ground. That explains the big spark because starter motors of course draw a lot of current. If that is what happened, buy a brand new OEM starter from the dealer or, if the dealer offers this, a rebuilt starter through the dealer’s OEM rebuild program. If you desire that a certified mechanic resolve this, please simply request starter replacement and the responding certified mechanic will get the problem diagnosed and repaired for you. Please let us know if you have further concerns or questions as we are always here to help you.