faulty sensor possibly cam/crank/oxygen/temperature sensor.
you could get a tummy ache.
If the 2003 Focus is running good then suddenly shakes and looses power, check the fuel system for proper pressure. If the pressure is correct, check the ignition system for fire, the ignition components could be starting to fail.
sounds like the ignition control module
Ending or remedy to a problem or could refer to focus on computer monitor.
Yes they could along with many other possibilities.
The belt breaking would be the problem. Investigate why it broke.
could be the regulator
You need to seek a professional. There could be a multitude of problems. You could have a loose part in the engine bay, or you could have an oil problem, or you could have a transmission problem, anything. I would personally say you have sludge in your engine, depends on mileage and how you drive it. Of course I don't own a Focus. Again more reason to seek a professional.
The fan or water pump,
What can cause the RPM on a car to jump while driving is a problem with the transmission. It could be a problem with the gears in the transmission itself.
You probably have a flyback/voltage tripler/focus block that has gone bad in the monitor. Replace the monitor.
it is due to video driver problem , it could be electricity or voltage problem or sometime you switch it on or off suddenly that is why it happens now resolve it by your hardware programmer. Regards