Dragging brakes, low coolant temperature, (thermostat), cylinder misfire, leaking injector, stretched timing chain, excessive fuel pressure, low compression, ...
If the problem is related to the air / fuel mixture, there should be a diagnostic fault code set in the Engine Computer. Any code that relates to something that could adversely affect emissions is supposed to turn on the Check Engine light. Even if the light isn't on, the place to start is by having the fault codes read. Many auto parts stores will do that for you for free.
Next is to use a scanner to view live data. In particular, the short and long-term fuel trim numbers will tell you if the computer is adding or subtracting fuel from the pre-programmed calculations. Then it becomes a matter of figuring out why there's too much fuel, or why the computer isn't having success adjusting the mixture.
If no cause is found related to engine performance, look at mechanical things like a dragging brake or low tire pressure.
Saturday, August 23rd, 2014 AT 1:38 AM