I'm having the same issue for about 3 weeks now. My car is a manual and whenever I put it in neutral, it hangs at 1,500 rpm for about 5 seconds and then drops off. Last week, the car would not start (tried 4 times - cranked perfectly, but no start). I let it sit for 15 minutes and it started but the check engine light was lit up. I removed the engine cover and reinstalled and the problem went away for about 5 days and is now back.

How does one "clean the cats"? Thanks for this post Selbyl