Loose or dirty wiring connection would be the most likely reason if it "fixed" itself. The issue is finding it when it is an intermittent problem. You mention cleaning the positive connector. If you removed it to clean it, that could have reset the ECM so it now idles correctly. I would clean every connector by opening it, spraying some contact cleaner and re-seating it, look for corrosion or loose pins. Then wait and see if it does it again.
And that is how some issues occur, you turn the key and the battery voltage hits a marginal connection or component and it stops functioning. Other issues are simply caused by wear and time.
Friday, April 14th, 2017 AT 6:32 AM