Weirdest thing.I have a '91 Civic and i drive for about 10 min. and the Check engine light comes on. So I turn off the car and try to read the code and it's gone! I restart the car and it's gone too. So another 10 min go by and same thing. I dont even wait a min to turn the car back on and it keeps doing it.I'm having issues with passing SMOG. I just cleaned out the EGR and I'm thinking MAP sensor now. Someone mentioned Catalytic Converter. But there is just no way to know! grrrrWhat would cause something to fail after warming up and then restarting after a cool down/restart?