91 oldsmobile cutlass ciera dies while trying to start

I was out driving and it ran fine for a good 30 miles and stopped at a grocery store to get groceries came back out and car wont start. It cranks just fine then goes into some crazy high idle and then dies 3 seconds later. If you give it some gas it will just stay high idle and then die. The first time it died it seemed like the exhaust came out the engine bay but i dont think the cat is clogged due to it running fine previously. Any ideas? Also the other day came out and no power or nothing and popped the hood nothing seemed out of the usual and then it started working again but died when driving no power or nothing. Not sure if the issues are related though. Replaced the alternator last month also
Edit/Delete Message