Sometime my car's steering seems to be very stiff, and the throttle is heavy.

What do you guys think is the problem?

 

Stiff steering could be due to a bad steering pump: it is either leaking or broken. As for heavy throttle, you are going to have to explain a bit better than that.

 

Hmmm.... my sister's cadillac has the same problem.
The mechanic says that it's the rack and pinion.
Whatever that might be. The only time the power steering works
is when the foot is on the gas. Pretty weird.
But hey, it's a cadillac not a mazda.