While every vehicle can have a steering problem, smaller cars tend to have more severe steering issues than larger vehicles. Part of the reason is mass: smaller cars have smaller, lighter suspension components, wheels, and tires, and as a result, they're more vulnerable to damage from potholes, curbs, etc. Part of the reason is that small cars are often designed to be as affordable as possible, and the steering systems aren't always as robust as they are in larger vehicles.
In any case, if you're experiencing a problem with your steering system on your Ford Focus, here's some info that might help you get a diagnosis:
Problem: The car "pulls" hard to the right when you really get on the gas.
Odds are, if your Focus seems to want to steer right when you really get on the gas, you're experiencing torque steer. If you've got a high-powered Focus ST - or a Focus with some awesome after-market power add-ons - you might just have to live with torque steer as part of owning your high-performance car. At some level, torque steer is an inevitable consequence of driving an FWD car with a lot of power.
But if you've got a normal, unmodified car, torque steer is a symptom of a handful of problems:
- After-market wheels can sometimes be to blame, depending on their size
- Uneven inflation in your tires and/or uneven wear
- An alignment issue
- Loose or worn parts in the steering rack, linkage, or bearings
If you're experiencing torque steer, it's a good idea to check your tire pressure and then look over your suspension system for looseness or play (or mention it to your auto mechanic so they can check it).
Problem: The steering "jumps" in an unpredictable direction every time you hit a bump of some kind.
A car that steers itself after hitting a bump has a "bump steer" problem. Usually, this problem is caused by a suspension modification. However, it can also be caused by a suspension that's been somehow damaged, perhaps by road debris.
If your Focus has a modified suspension, you'll want to look into a bump steer kit for your vehicle and/or contact the manufacturer of your suspension kit for advice (they'll likely have a recommended process for addressing bump steer issues caused by their kit). If your Focus does not have a modified suspension, get underneath and look for damage and/or get your vehicle checked out ASAP. If, for example, you have a bent tie rod, you could potentially lose control of your car.
Problem: The steering feels really heavy and hard to turn.
If you have an older Focus (2009 or older), your power steering system is hydraulic. Heavy feel in a hydraulic system can be tough to diagnose...could be something as simple as insufficient steering fluid, or it could be a symptom of a more serious steering rack problem. It's something you definitely want to have checked out, as steering problems tend to get more expensive to fix the longer you ignore them.
If you've got a newer Focus (2010+), your steering system is electrically operated. A heavy feeling is symptomatic of an electrical failure somewhere (perhaps just a poorly functioning sensor, perhaps more), and according to some forum posts, this problem is somewhat common. You can use your scanning tool to check your engine for codes, and you can also ask your local Ford dealer about any pending TSBs on your Focus (Ford has issued a couple dealing with this issue).