Originally Posted by mmmoose
What you're describing is a feature that's common for electronic power steering. It sounds to me like you're used to older cars which use hydraulic assisted steering, where the steering is either loose or tight all the time. With electronic power steering the level of assist the electronic motor applies is proportional to the speed you're traveling.
You can test this out by going to a parking lot and driving around at a very slow speed (~10 mph). Do a few turns and notice how the steering wheel is very loose and easy to turn. Now drive off onto a main road and speed up a bit. As you get closer to 35+ mph, the steering wheel will gradually tighten and become more responsive. This is 100% completely normal with electronic power steering systems.
I can't explain the zig-zagging that you describe, because I don't know if you're naturally overcompensating for a steering system you're not used to. But I think a quick way to figure out whether it's really a problem or not is to visit your dealership and test drive another Focus (or another Ford model) to see if it really is the steering system. I don't want to discredit you entirely because maybe you really may be onto something. But I just figured I'd explain how newer steering systems work.
I can tell you right now that almost all cars that use electronic power steering have speed proportional assist. It took me a while for me to get used to it too when I bought the Rabbit. Sport trim cars (GTI, MazdaSpeed3, etc.) have their assist levels turned a little lower to emulate old school hydraulic power steering responsiveness (which is probably what you're more used to). I'd rather have that feeling too, but unfortunately these cars have steering that's tuned more for comfort rather than precision.
The good news is that the level of assist can be tweaked very easily. People who work for Ford can use a diagnostic tool hooked up to your car's computer to actually change the value of the level of assist (much like changing the mouse sensitivity on your computer). The bad news is that your dealership probably won't let you do it by request. Believe me I've tried to get them to set mine to a sportier setting (GTI's default value) and they refused even when I attempted to bribe them, stating liability reasons.
mmmoose, thank you for your response offering me a driving lesson by explaining the difference between electronic assist and hydraulic power steering; as if I understood how electronic assist worked, then there would not be a problem with the steering. Obviously, I need to explain in more detail. As I said in my first attempt to explain the problem, it is not when
the car reaches 60 to 65 mph (if that was the case, I could understand what was going on), but after some distance at that speed. I wonder (I am guessing) if when the car senses no activity, such as on a straight-a-way where there is no correction going on to keep the car straight, then maybe the electronic assist shuts down to save on power for better gas mileage. Now, that's when the steering gets stiff. So when you need to correct it to stay centered in the lane, it takes more pressure to turn the steering wheel, then for an instant, the electronic assist kicks in, the steering loosens up, and the car darts in the direction you were correcting it to go. Then it stiffens up right away, so when you correct it back, the process repeats. So I find myself zig-zagging down the lane. Now I find that if I move the steering wheel back and forth rapidly for a few times (not swerving the car, just shaking the steering wheel left-to-right slightly) I can make the car stop acting up and it will drive fine...sometimes for a long distance, sometimes for a short distance. It's like I have to wake up the steering so it will respond normally without jerking when you try to correct it. I hope this is a better explanation of what's going on with the steering.