I have a ls/vtec turbo hatch and it ran great. but all of the sudden the other day I went to hit the gas and the car went no where and sounded like it was detonating. when I looked at my stock rpm gauge the needle was bouncing around from 7-4-5-3-7 again but when I looked at my autometer tack the rpm's where fine just the stock tack was doing this. when I pulled over the car's idle was at 600 instead of 800. when I turned the car off and then back on it ran fine but after 5 minutes it starts doing it again. has anyone ever had this problem or know what it could be?