Tachometer drops to 0 at highway speeds and mpg also drop
While traveling at highway speeds my engine will feel like it misses for about 1 second and then the tachometer drops to zero and stays there until the engine is restarted. Also the gas mileage will drop from about 30 mpg to 25 mpg. The car continues to perform ok at highway speeds other than it is burning more gas then it should. This problem has happened about 4 times in the last 2 months. Any ideas of what is causing this?