I have a 1991 honda civic dx. Worked great until last week when I was stopped at a red light and the engine just cut out. Restarted OK. Then I was cruising down the freeway and the engine suddenly cut out again. I pulled over into the shoulder and it started fine. Now, I can't make a 5 minute trip to the store without it cutting out, and it takes a few tries to start. My mechanic cannot locate the cause. Anyone?