Hello, all. This is my first post.I wasn't sure where else to turn for advice on this matter. I hope someone can help.

I have a 1994 Cavalier. The check engine light comes on every once in a while. I can never predict when it'll come on -usually during or after some highway driving. Whenthe check engine light*does* come on, the engine makes a different noise. And when you shut the engine off after the check engine light has been on it sounds like a jet engine powering down.Normally, the engine shuts off right quick. But when the check engine light's been on, the engine will makea spinning"powering down" noise for 5 to 7 seconds after I've turned the key to "off." Very odd. It's like something spinning came out of its socket and made the check engine light go off. Any ideas what's going on? It only happens once in a while, but it's certainly something I'd like to get checked out.

 

Sorry. Forgot to mention it's an automatic transmission. Thanks.