After I change a new starter for my car, all of the problems are gone.
So, just change it. It's not an expensive work.How can I tell if my starter is going bad?It's easy in this situation to blame the starter, and most likely it is the culprit. Instead of purchasing a new starter right away and taking the time to install it have the old one tested.
I believe the starter is fairly easy to remove on the Focus. A few bolts, 2 wires and most likely a sending wire from the ignition switch. After removed almost any auto parts store will test it for you and if it's bad you can avoid the core charge by already having the part with you.
The intermittent service and the duration of your symptoms leads me to believe you may just have a bad ground. If the starter tests good this is where I would put my energy, if it tests bad...you know what to do.
The world of automotive electrical is a tricky one, the problem could lead all the way back to the ignition switch, relay, or solenoid. It's a road you probably don't want to go down if you have little experience with automotive repair. Test the parts before you replace them and don't allow a mechanic to just start replacing parts in an effort to diagnose the problem.
One other item to keep in mind that could help you diagnose the problem for free is the pulling of system codes. Most vehicles will register an error code without throwing up any lights in the cabin (weird I know), take it to an auto parts store and ask them to %26quot;pull the codes%26quot; for you..it's free. If you're lucky there will be none....but why waste money when you don't have to?