99 intrepid strange noise/ knock no start?

I have a 99 intrepid with a 2.7 v6. Started it up which it has always had to crank just longer than normal, it started fine but was making knock noise almost like low oil. I drove to gas station which is less than a mile away. I was afraid to drive fast cause noise did get louder going faster and when I got to gas station it sounded almost like knocking/rubberband almost breaking noise. I turned car off and checked oil, I was 2 quarts low. I added oil and tried to start but it just turns over. When turning over it sounds fine. No lights and no trouble codes. Strange cause engine light was on for 6 months due to catalytic converter being plugged. And now the past week light has magically stayed off and I haven't fixed it. I know a converter could cause it to not run. But make that noise? Serpetine belts good.. any ideas of what it could be? Thank you